diff --git a/doc/whats-new.rst b/doc/whats-new.rst
index 4d4291e050e..74c7104117a 100644
--- a/doc/whats-new.rst
+++ b/doc/whats-new.rst
@@ -82,6 +82,8 @@ Documentation
 Internal Changes
 ~~~~~~~~~~~~~~~~
 
+- Enable typing checks of pandas (:pull:`9213`).
+  By `Michael Niklas <https://github.com/headtr1ck>`_.
 
 .. _whats-new.2024.06.0:
 
diff --git a/pyproject.toml b/pyproject.toml
index 4704751b445..3eafcda7670 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -120,7 +120,6 @@ module = [
   "netCDF4.*",
   "netcdftime.*",
   "opt_einsum.*",
-  "pandas.*",
   "pint.*",
   "pooch.*",
   "pyarrow.*",
diff --git a/xarray/coding/cftime_offsets.py b/xarray/coding/cftime_offsets.py
index c2712569782..9dbc60ef0f3 100644
--- a/xarray/coding/cftime_offsets.py
+++ b/xarray/coding/cftime_offsets.py
@@ -43,9 +43,10 @@
 from __future__ import annotations
 
 import re
+from collections.abc import Mapping
 from datetime import datetime, timedelta
 from functools import partial
-from typing import TYPE_CHECKING, ClassVar
+from typing import TYPE_CHECKING, ClassVar, Literal
 
 import numpy as np
 import pandas as pd
@@ -74,7 +75,10 @@
 
 
 if TYPE_CHECKING:
-    from xarray.core.types import InclusiveOptions, SideOptions
+    from xarray.core.types import InclusiveOptions, Self, SideOptions, TypeAlias
+
+
+DayOption: TypeAlias = Literal["start", "end"]
 
 
 def _nanosecond_precision_timestamp(*args, **kwargs):
@@ -109,9 +113,10 @@ def get_date_type(calendar, use_cftime=True):
 
 class BaseCFTimeOffset:
     _freq: ClassVar[str | None] = None
-    _day_option: ClassVar[str | None] = None
+    _day_option: ClassVar[DayOption | None] = None
+    n: int
 
-    def __init__(self, n: int = 1):
+    def __init__(self, n: int = 1) -> None:
         if not isinstance(n, int):
             raise TypeError(
                 "The provided multiple 'n' must be an integer. "
@@ -119,13 +124,15 @@ def __init__(self, n: int = 1):
             )
         self.n = n
 
-    def rule_code(self):
+    def rule_code(self) -> str | None:
         return self._freq
 
-    def __eq__(self, other):
+    def __eq__(self, other: object) -> bool:
+        if not isinstance(other, BaseCFTimeOffset):
+            return NotImplemented
         return self.n == other.n and self.rule_code() == other.rule_code()
 
-    def __ne__(self, other):
+    def __ne__(self, other: object) -> bool:
         return not self == other
 
     def __add__(self, other):
@@ -142,12 +149,12 @@ def __sub__(self, other):
         else:
             return NotImplemented
 
-    def __mul__(self, other):
+    def __mul__(self, other: int) -> Self:
         if not isinstance(other, int):
             return NotImplemented
         return type(self)(n=other * self.n)
 
-    def __neg__(self):
+    def __neg__(self) -> Self:
         return self * -1
 
     def __rmul__(self, other):
@@ -161,10 +168,10 @@ def __rsub__(self, other):
             raise TypeError("Cannot subtract cftime offsets of differing types")
         return -self + other
 
-    def __apply__(self):
+    def __apply__(self, other):
         return NotImplemented
 
-    def onOffset(self, date):
+    def onOffset(self, date) -> bool:
         """Check if the given date is in the set of possible dates created
         using a length-one version of this offset class."""
         test_date = (self + date) - self
@@ -197,22 +204,21 @@ def _get_offset_day(self, other):
 class Tick(BaseCFTimeOffset):
     # analogous https://github.com/pandas-dev/pandas/blob/ccb25ab1d24c4fb9691270706a59c8d319750870/pandas/_libs/tslibs/offsets.pyx#L806
 
-    def _next_higher_resolution(self):
+    def _next_higher_resolution(self) -> Tick:
         self_type = type(self)
-        if self_type not in [Day, Hour, Minute, Second, Millisecond]:
-            raise ValueError("Could not convert to integer offset at any resolution")
-        if type(self) is Day:
+        if self_type is Day:
             return Hour(self.n * 24)
-        if type(self) is Hour:
+        if self_type is Hour:
             return Minute(self.n * 60)
-        if type(self) is Minute:
+        if self_type is Minute:
             return Second(self.n * 60)
-        if type(self) is Second:
+        if self_type is Second:
             return Millisecond(self.n * 1000)
-        if type(self) is Millisecond:
+        if self_type is Millisecond:
             return Microsecond(self.n * 1000)
+        raise ValueError("Could not convert to integer offset at any resolution")
 
-    def __mul__(self, other):
+    def __mul__(self, other: int | float) -> Tick:
         if not isinstance(other, (int, float)):
             return NotImplemented
         if isinstance(other, float):
@@ -227,12 +233,12 @@ def __mul__(self, other):
             return new_self * other
         return type(self)(n=other * self.n)
 
-    def as_timedelta(self):
+    def as_timedelta(self) -> timedelta:
         """All Tick subclasses must implement an as_timedelta method."""
         raise NotImplementedError
 
 
-def _get_day_of_month(other, day_option):
+def _get_day_of_month(other, day_option: DayOption) -> int:
     """Find the day in `other`'s month that satisfies a BaseCFTimeOffset's
     onOffset policy, as described by the `day_option` argument.
 
@@ -251,14 +257,13 @@ def _get_day_of_month(other, day_option):
 
     if day_option == "start":
         return 1
-    elif day_option == "end":
+    if day_option == "end":
         return _days_in_month(other)
-    elif day_option is None:
+    if day_option is None:
         # Note: unlike `_shift_month`, _get_day_of_month does not
         # allow day_option = None
         raise NotImplementedError()
-    else:
-        raise ValueError(day_option)
+    raise ValueError(day_option)
 
 
 def _days_in_month(date):
@@ -293,7 +298,7 @@ def _adjust_n_years(other, n, month, reference_day):
     return n
 
 
-def _shift_month(date, months, day_option="start"):
+def _shift_month(date, months, day_option: DayOption = "start"):
     """Shift the date to a month start or end a given number of months away."""
     if cftime is None:
         raise ModuleNotFoundError("No module named 'cftime'")
@@ -316,7 +321,9 @@ def _shift_month(date, months, day_option="start"):
     return date.replace(year=year, month=month, day=day)
 
 
-def roll_qtrday(other, n, month, day_option, modby=3):
+def roll_qtrday(
+    other, n: int, month: int, day_option: DayOption, modby: int = 3
+) -> int:
     """Possibly increment or decrement the number of periods to shift
     based on rollforward/rollbackward conventions.
 
@@ -357,7 +364,7 @@ def roll_qtrday(other, n, month, day_option, modby=3):
     return n
 
 
-def _validate_month(month, default_month):
+def _validate_month(month: int | None, default_month: int) -> int:
     result_month = default_month if month is None else month
     if not isinstance(result_month, int):
         raise TypeError(
@@ -381,7 +388,7 @@ def __apply__(self, other):
         n = _adjust_n_months(other.day, self.n, 1)
         return _shift_month(other, n, "start")
 
-    def onOffset(self, date):
+    def onOffset(self, date) -> bool:
         """Check if the given date is in the set of possible dates created
         using a length-one version of this offset class."""
         return date.day == 1
@@ -394,7 +401,7 @@ def __apply__(self, other):
         n = _adjust_n_months(other.day, self.n, _days_in_month(other))
         return _shift_month(other, n, "end")
 
-    def onOffset(self, date):
+    def onOffset(self, date) -> bool:
         """Check if the given date is in the set of possible dates created
         using a length-one version of this offset class."""
         return date.day == _days_in_month(date)
@@ -419,10 +426,10 @@ def onOffset(self, date):
 class QuarterOffset(BaseCFTimeOffset):
     """Quarter representation copied off of pandas/tseries/offsets.py"""
 
-    _freq: ClassVar[str]
     _default_month: ClassVar[int]
+    month: int
 
-    def __init__(self, n=1, month=None):
+    def __init__(self, n: int = 1, month: int | None = None) -> None:
         BaseCFTimeOffset.__init__(self, n)
         self.month = _validate_month(month, self._default_month)
 
@@ -439,29 +446,28 @@ def __apply__(self, other):
         months = qtrs * 3 - months_since
         return _shift_month(other, months, self._day_option)
 
-    def onOffset(self, date):
+    def onOffset(self, date) -> bool:
         """Check if the given date is in the set of possible dates created
         using a length-one version of this offset class."""
         mod_month = (date.month - self.month) % 3
         return mod_month == 0 and date.day == self._get_offset_day(date)
 
-    def __sub__(self, other):
+    def __sub__(self, other: Self) -> Self:
         if cftime is None:
             raise ModuleNotFoundError("No module named 'cftime'")
 
         if isinstance(other, cftime.datetime):
             raise TypeError("Cannot subtract cftime.datetime from offset.")
-        elif type(other) == type(self) and other.month == self.month:
+        if type(other) == type(self) and other.month == self.month:
             return type(self)(self.n - other.n, month=self.month)
-        else:
-            return NotImplemented
+        return NotImplemented
 
     def __mul__(self, other):
         if isinstance(other, float):
             return NotImplemented
         return type(self)(n=other * self.n, month=self.month)
 
-    def rule_code(self):
+    def rule_code(self) -> str:
         return f"{self._freq}-{_MONTH_ABBREVIATIONS[self.month]}"
 
     def __str__(self):
@@ -519,11 +525,10 @@ def rollback(self, date):
 
 
 class YearOffset(BaseCFTimeOffset):
-    _freq: ClassVar[str]
-    _day_option: ClassVar[str]
     _default_month: ClassVar[int]
+    month: int
 
-    def __init__(self, n=1, month=None):
+    def __init__(self, n: int = 1, month: int | None = None) -> None:
         BaseCFTimeOffset.__init__(self, n)
         self.month = _validate_month(month, self._default_month)
 
@@ -549,10 +554,10 @@ def __mul__(self, other):
             return NotImplemented
         return type(self)(n=other * self.n, month=self.month)
 
-    def rule_code(self):
+    def rule_code(self) -> str:
         return f"{self._freq}-{_MONTH_ABBREVIATIONS[self.month]}"
 
-    def __str__(self):
+    def __str__(self) -> str:
         return f"<{type(self).__name__}: n={self.n}, month={self.month}>"
 
 
@@ -561,7 +566,7 @@ class YearBegin(YearOffset):
     _day_option = "start"
     _default_month = 1
 
-    def onOffset(self, date):
+    def onOffset(self, date) -> bool:
         """Check if the given date is in the set of possible dates created
         using a length-one version of this offset class."""
         return date.day == 1 and date.month == self.month
@@ -586,7 +591,7 @@ class YearEnd(YearOffset):
     _day_option = "end"
     _default_month = 12
 
-    def onOffset(self, date):
+    def onOffset(self, date) -> bool:
         """Check if the given date is in the set of possible dates created
         using a length-one version of this offset class."""
         return date.day == _days_in_month(date) and date.month == self.month
@@ -609,7 +614,7 @@ def rollback(self, date):
 class Day(Tick):
     _freq = "D"
 
-    def as_timedelta(self):
+    def as_timedelta(self) -> timedelta:
         return timedelta(days=self.n)
 
     def __apply__(self, other):
@@ -619,7 +624,7 @@ def __apply__(self, other):
 class Hour(Tick):
     _freq = "h"
 
-    def as_timedelta(self):
+    def as_timedelta(self) -> timedelta:
         return timedelta(hours=self.n)
 
     def __apply__(self, other):
@@ -629,7 +634,7 @@ def __apply__(self, other):
 class Minute(Tick):
     _freq = "min"
 
-    def as_timedelta(self):
+    def as_timedelta(self) -> timedelta:
         return timedelta(minutes=self.n)
 
     def __apply__(self, other):
@@ -639,7 +644,7 @@ def __apply__(self, other):
 class Second(Tick):
     _freq = "s"
 
-    def as_timedelta(self):
+    def as_timedelta(self) -> timedelta:
         return timedelta(seconds=self.n)
 
     def __apply__(self, other):
@@ -649,7 +654,7 @@ def __apply__(self, other):
 class Millisecond(Tick):
     _freq = "ms"
 
-    def as_timedelta(self):
+    def as_timedelta(self) -> timedelta:
         return timedelta(milliseconds=self.n)
 
     def __apply__(self, other):
@@ -659,30 +664,32 @@ def __apply__(self, other):
 class Microsecond(Tick):
     _freq = "us"
 
-    def as_timedelta(self):
+    def as_timedelta(self) -> timedelta:
         return timedelta(microseconds=self.n)
 
     def __apply__(self, other):
         return other + self.as_timedelta()
 
 
-def _generate_anchored_offsets(base_freq, offset):
-    offsets = {}
+def _generate_anchored_offsets(
+    base_freq: str, offset: type[YearOffset | QuarterOffset]
+) -> dict[str, type[BaseCFTimeOffset]]:
+    offsets: dict[str, type[BaseCFTimeOffset]] = {}
     for month, abbreviation in _MONTH_ABBREVIATIONS.items():
         anchored_freq = f"{base_freq}-{abbreviation}"
-        offsets[anchored_freq] = partial(offset, month=month)
+        offsets[anchored_freq] = partial(offset, month=month)  # type: ignore[assignment]
     return offsets
 
 
-_FREQUENCIES = {
+_FREQUENCIES: Mapping[str, type[BaseCFTimeOffset]] = {
     "A": YearEnd,
     "AS": YearBegin,
     "Y": YearEnd,
     "YE": YearEnd,
     "YS": YearBegin,
-    "Q": partial(QuarterEnd, month=12),
-    "QE": partial(QuarterEnd, month=12),
-    "QS": partial(QuarterBegin, month=1),
+    "Q": partial(QuarterEnd, month=12),  # type: ignore[dict-item]
+    "QE": partial(QuarterEnd, month=12),  # type: ignore[dict-item]
+    "QS": partial(QuarterBegin, month=1),  # type: ignore[dict-item]
     "M": MonthEnd,
     "ME": MonthEnd,
     "MS": MonthBegin,
@@ -717,7 +724,9 @@ def _generate_anchored_offsets(base_freq, offset):
 CFTIME_TICKS = (Day, Hour, Minute, Second)
 
 
-def _generate_anchored_deprecated_frequencies(deprecated, recommended):
+def _generate_anchored_deprecated_frequencies(
+    deprecated: str, recommended: str
+) -> dict[str, str]:
     pairs = {}
     for abbreviation in _MONTH_ABBREVIATIONS.values():
         anchored_deprecated = f"{deprecated}-{abbreviation}"
@@ -726,7 +735,7 @@ def _generate_anchored_deprecated_frequencies(deprecated, recommended):
     return pairs
 
 
-_DEPRECATED_FREQUENICES = {
+_DEPRECATED_FREQUENICES: dict[str, str] = {
     "A": "YE",
     "Y": "YE",
     "AS": "YS",
@@ -759,16 +768,16 @@ def _emit_freq_deprecation_warning(deprecated_freq):
     emit_user_level_warning(message, FutureWarning)
 
 
-def to_offset(freq, warn=True):
+def to_offset(freq: BaseCFTimeOffset | str, warn: bool = True) -> BaseCFTimeOffset:
     """Convert a frequency string to the appropriate subclass of
     BaseCFTimeOffset."""
     if isinstance(freq, BaseCFTimeOffset):
         return freq
-    else:
-        try:
-            freq_data = re.match(_PATTERN, freq).groupdict()
-        except AttributeError:
-            raise ValueError("Invalid frequency string provided")
+
+    match = re.match(_PATTERN, freq)
+    if match is None:
+        raise ValueError("Invalid frequency string provided")
+    freq_data = match.groupdict()
 
     freq = freq_data["freq"]
     if warn and freq in _DEPRECATED_FREQUENICES:
@@ -909,7 +918,9 @@ def _translate_closed_to_inclusive(closed):
     return inclusive
 
 
-def _infer_inclusive(closed, inclusive):
+def _infer_inclusive(
+    closed: NoDefault | SideOptions, inclusive: InclusiveOptions | None
+) -> InclusiveOptions:
     """Follows code added in pandas #43504."""
     if closed is not no_default and inclusive is not None:
         raise ValueError(
@@ -917,9 +928,9 @@ def _infer_inclusive(closed, inclusive):
             "passed if argument `inclusive` is not None."
         )
     if closed is not no_default:
-        inclusive = _translate_closed_to_inclusive(closed)
-    elif inclusive is None:
-        inclusive = "both"
+        return _translate_closed_to_inclusive(closed)
+    if inclusive is None:
+        return "both"
     return inclusive
 
 
@@ -933,7 +944,7 @@ def cftime_range(
     closed: NoDefault | SideOptions = no_default,
     inclusive: None | InclusiveOptions = None,
     calendar="standard",
-):
+) -> CFTimeIndex:
     """Return a fixed frequency CFTimeIndex.
 
     Parameters
diff --git a/xarray/coding/cftimeindex.py b/xarray/coding/cftimeindex.py
index 6898809e3b0..cd902257902 100644
--- a/xarray/coding/cftimeindex.py
+++ b/xarray/coding/cftimeindex.py
@@ -45,6 +45,7 @@
 import re
 import warnings
 from datetime import timedelta
+from typing import TYPE_CHECKING, Any
 
 import numpy as np
 import pandas as pd
@@ -64,6 +65,10 @@
 except ImportError:
     cftime = None
 
+if TYPE_CHECKING:
+    from xarray.coding.cftime_offsets import BaseCFTimeOffset
+    from xarray.core.types import Self
+
 
 # constants for cftimeindex.repr
 CFTIME_REPR_LENGTH = 19
@@ -495,7 +500,7 @@ def get_value(self, series, key):
         else:
             return series.iloc[self.get_loc(key)]
 
-    def __contains__(self, key):
+    def __contains__(self, key: Any) -> bool:
         """Adapted from
         pandas.tseries.base.DatetimeIndexOpsMixin.__contains__"""
         try:
@@ -503,16 +508,20 @@ def __contains__(self, key):
             return (
                 is_scalar(result)
                 or type(result) == slice
-                or (isinstance(result, np.ndarray) and result.size)
+                or (isinstance(result, np.ndarray) and result.size > 0)
             )
         except (KeyError, TypeError, ValueError):
             return False
 
-    def contains(self, key):
+    def contains(self, key: Any) -> bool:
         """Needed for .loc based partial-string indexing"""
         return self.__contains__(key)
 
-    def shift(self, n: int | float, freq: str | timedelta):
+    def shift(  # type: ignore[override]  # freq is typed Any, we are more precise
+        self,
+        periods: int | float,
+        freq: str | timedelta | BaseCFTimeOffset | None = None,
+    ) -> Self:
         """Shift the CFTimeIndex a multiple of the given frequency.
 
         See the documentation for :py:func:`~xarray.cftime_range` for a
@@ -520,9 +529,9 @@ def shift(self, n: int | float, freq: str | timedelta):
 
         Parameters
         ----------
-        n : int, float if freq of days or below
+        periods : int, float if freq of days or below
             Periods to shift by
-        freq : str or datetime.timedelta
+        freq : str, datetime.timedelta or BaseCFTimeOffset
             A frequency string or datetime.timedelta object to shift by
 
         Returns
@@ -546,33 +555,42 @@ def shift(self, n: int | float, freq: str | timedelta):
         CFTimeIndex([2000-02-01 12:00:00],
                     dtype='object', length=1, calendar='standard', freq=None)
         """
-        if isinstance(freq, timedelta):
-            return self + n * freq
-        elif isinstance(freq, str):
-            from xarray.coding.cftime_offsets import to_offset
+        from xarray.coding.cftime_offsets import BaseCFTimeOffset
 
-            return self + n * to_offset(freq)
-        else:
+        if freq is None:
+            # None type is required to be compatible with base pd.Index class
             raise TypeError(
-                f"'freq' must be of type str or datetime.timedelta, got {freq}."
+                f"`freq` argument cannot be None for {type(self).__name__}.shift"
             )
 
-    def __add__(self, other):
+        if isinstance(freq, timedelta):
+            return self + periods * freq
+
+        if isinstance(freq, (str, BaseCFTimeOffset)):
+            from xarray.coding.cftime_offsets import to_offset
+
+            return self + periods * to_offset(freq)
+
+        raise TypeError(
+            f"'freq' must be of type str or datetime.timedelta, got {type(freq)}."
+        )
+
+    def __add__(self, other) -> Self:
         if isinstance(other, pd.TimedeltaIndex):
             other = other.to_pytimedelta()
-        return CFTimeIndex(np.array(self) + other)
+        return type(self)(np.array(self) + other)
 
-    def __radd__(self, other):
+    def __radd__(self, other) -> Self:
         if isinstance(other, pd.TimedeltaIndex):
             other = other.to_pytimedelta()
-        return CFTimeIndex(other + np.array(self))
+        return type(self)(other + np.array(self))
 
     def __sub__(self, other):
         if _contains_datetime_timedeltas(other):
-            return CFTimeIndex(np.array(self) - other)
-        elif isinstance(other, pd.TimedeltaIndex):
-            return CFTimeIndex(np.array(self) - other.to_pytimedelta())
-        elif _contains_cftime_datetimes(np.array(other)):
+            return type(self)(np.array(self) - other)
+        if isinstance(other, pd.TimedeltaIndex):
+            return type(self)(np.array(self) - other.to_pytimedelta())
+        if _contains_cftime_datetimes(np.array(other)):
             try:
                 return pd.TimedeltaIndex(np.array(self) - np.array(other))
             except OUT_OF_BOUNDS_TIMEDELTA_ERRORS:
@@ -580,8 +598,7 @@ def __sub__(self, other):
                     "The time difference exceeds the range of values "
                     "that can be expressed at the nanosecond resolution."
                 )
-        else:
-            return NotImplemented
+        return NotImplemented
 
     def __rsub__(self, other):
         try:
diff --git a/xarray/coding/times.py b/xarray/coding/times.py
index 50a2ba93c09..badb9259b06 100644
--- a/xarray/coding/times.py
+++ b/xarray/coding/times.py
@@ -5,7 +5,7 @@
 from collections.abc import Hashable
 from datetime import datetime, timedelta
 from functools import partial
-from typing import TYPE_CHECKING, Callable, Union
+from typing import Callable, Literal, Union, cast
 
 import numpy as np
 import pandas as pd
@@ -36,10 +36,9 @@
 except ImportError:
     cftime = None
 
-if TYPE_CHECKING:
-    from xarray.core.types import CFCalendar, T_DuckArray
+from xarray.core.types import CFCalendar, NPDatetimeUnitOptions, T_DuckArray
 
-    T_Name = Union[Hashable, None]
+T_Name = Union[Hashable, None]
 
 # standard calendars recognized by cftime
 _STANDARD_CALENDARS = {"standard", "gregorian", "proleptic_gregorian"}
@@ -111,22 +110,25 @@ def _is_numpy_compatible_time_range(times):
         return True
 
 
-def _netcdf_to_numpy_timeunit(units: str) -> str:
+def _netcdf_to_numpy_timeunit(units: str) -> NPDatetimeUnitOptions:
     units = units.lower()
     if not units.endswith("s"):
         units = f"{units}s"
-    return {
-        "nanoseconds": "ns",
-        "microseconds": "us",
-        "milliseconds": "ms",
-        "seconds": "s",
-        "minutes": "m",
-        "hours": "h",
-        "days": "D",
-    }[units]
+    return cast(
+        NPDatetimeUnitOptions,
+        {
+            "nanoseconds": "ns",
+            "microseconds": "us",
+            "milliseconds": "ms",
+            "seconds": "s",
+            "minutes": "m",
+            "hours": "h",
+            "days": "D",
+        }[units],
+    )
 
 
-def _numpy_to_netcdf_timeunit(units: str) -> str:
+def _numpy_to_netcdf_timeunit(units: NPDatetimeUnitOptions) -> str:
     return {
         "ns": "nanoseconds",
         "us": "microseconds",
@@ -252,12 +254,12 @@ def _decode_datetime_with_pandas(
             "pandas."
         )
 
-    time_units, ref_date = _unpack_netcdf_time_units(units)
+    time_units, ref_date_str = _unpack_netcdf_time_units(units)
     time_units = _netcdf_to_numpy_timeunit(time_units)
     try:
         # TODO: the strict enforcement of nanosecond precision Timestamps can be
         # relaxed when addressing GitHub issue #7493.
-        ref_date = nanosecond_precision_timestamp(ref_date)
+        ref_date = nanosecond_precision_timestamp(ref_date_str)
     except ValueError:
         # ValueError is raised by pd.Timestamp for non-ISO timestamp
         # strings, in which case we fall back to using cftime
@@ -471,6 +473,7 @@ def cftime_to_nptime(times, raise_on_invalid: bool = True) -> np.ndarray:
     # TODO: the strict enforcement of nanosecond precision datetime values can
     # be relaxed when addressing GitHub issue #7493.
     new = np.empty(times.shape, dtype="M8[ns]")
+    dt: pd.Timestamp | Literal["NaT"]
     for i, t in np.ndenumerate(times):
         try:
             # Use pandas.Timestamp in place of datetime.datetime, because
diff --git a/xarray/core/_typed_ops.py b/xarray/core/_typed_ops.py
index c1748e322c2..61aa1846bd0 100644
--- a/xarray/core/_typed_ops.py
+++ b/xarray/core/_typed_ops.py
@@ -11,15 +11,15 @@
 from xarray.core.types import (
     DaCompatible,
     DsCompatible,
-    GroupByCompatible,
     Self,
-    T_DataArray,
     T_Xarray,
     VarCompatible,
 )
 
 if TYPE_CHECKING:
+    from xarray.core.dataarray import DataArray
     from xarray.core.dataset import Dataset
+    from xarray.core.types import T_DataArray as T_DA
 
 
 class DatasetOpsMixin:
@@ -455,165 +455,165 @@ def _binary_op(
         raise NotImplementedError
 
     @overload
-    def __add__(self, other: T_DataArray) -> T_DataArray: ...
+    def __add__(self, other: T_DA) -> T_DA: ...
 
     @overload
     def __add__(self, other: VarCompatible) -> Self: ...
 
-    def __add__(self, other: VarCompatible) -> Self | T_DataArray:
+    def __add__(self, other: VarCompatible) -> Self | T_DA:
         return self._binary_op(other, operator.add)
 
     @overload
-    def __sub__(self, other: T_DataArray) -> T_DataArray: ...
+    def __sub__(self, other: T_DA) -> T_DA: ...
 
     @overload
     def __sub__(self, other: VarCompatible) -> Self: ...
 
-    def __sub__(self, other: VarCompatible) -> Self | T_DataArray:
+    def __sub__(self, other: VarCompatible) -> Self | T_DA:
         return self._binary_op(other, operator.sub)
 
     @overload
-    def __mul__(self, other: T_DataArray) -> T_DataArray: ...
+    def __mul__(self, other: T_DA) -> T_DA: ...
 
     @overload
     def __mul__(self, other: VarCompatible) -> Self: ...
 
-    def __mul__(self, other: VarCompatible) -> Self | T_DataArray:
+    def __mul__(self, other: VarCompatible) -> Self | T_DA:
         return self._binary_op(other, operator.mul)
 
     @overload
-    def __pow__(self, other: T_DataArray) -> T_DataArray: ...
+    def __pow__(self, other: T_DA) -> T_DA: ...
 
     @overload
     def __pow__(self, other: VarCompatible) -> Self: ...
 
-    def __pow__(self, other: VarCompatible) -> Self | T_DataArray:
+    def __pow__(self, other: VarCompatible) -> Self | T_DA:
         return self._binary_op(other, operator.pow)
 
     @overload
-    def __truediv__(self, other: T_DataArray) -> T_DataArray: ...
+    def __truediv__(self, other: T_DA) -> T_DA: ...
 
     @overload
     def __truediv__(self, other: VarCompatible) -> Self: ...
 
-    def __truediv__(self, other: VarCompatible) -> Self | T_DataArray:
+    def __truediv__(self, other: VarCompatible) -> Self | T_DA:
         return self._binary_op(other, operator.truediv)
 
     @overload
-    def __floordiv__(self, other: T_DataArray) -> T_DataArray: ...
+    def __floordiv__(self, other: T_DA) -> T_DA: ...
 
     @overload
     def __floordiv__(self, other: VarCompatible) -> Self: ...
 
-    def __floordiv__(self, other: VarCompatible) -> Self | T_DataArray:
+    def __floordiv__(self, other: VarCompatible) -> Self | T_DA:
         return self._binary_op(other, operator.floordiv)
 
     @overload
-    def __mod__(self, other: T_DataArray) -> T_DataArray: ...
+    def __mod__(self, other: T_DA) -> T_DA: ...
 
     @overload
     def __mod__(self, other: VarCompatible) -> Self: ...
 
-    def __mod__(self, other: VarCompatible) -> Self | T_DataArray:
+    def __mod__(self, other: VarCompatible) -> Self | T_DA:
         return self._binary_op(other, operator.mod)
 
     @overload
-    def __and__(self, other: T_DataArray) -> T_DataArray: ...
+    def __and__(self, other: T_DA) -> T_DA: ...
 
     @overload
     def __and__(self, other: VarCompatible) -> Self: ...
 
-    def __and__(self, other: VarCompatible) -> Self | T_DataArray:
+    def __and__(self, other: VarCompatible) -> Self | T_DA:
         return self._binary_op(other, operator.and_)
 
     @overload
-    def __xor__(self, other: T_DataArray) -> T_DataArray: ...
+    def __xor__(self, other: T_DA) -> T_DA: ...
 
     @overload
     def __xor__(self, other: VarCompatible) -> Self: ...
 
-    def __xor__(self, other: VarCompatible) -> Self | T_DataArray:
+    def __xor__(self, other: VarCompatible) -> Self | T_DA:
         return self._binary_op(other, operator.xor)
 
     @overload
-    def __or__(self, other: T_DataArray) -> T_DataArray: ...
+    def __or__(self, other: T_DA) -> T_DA: ...
 
     @overload
     def __or__(self, other: VarCompatible) -> Self: ...
 
-    def __or__(self, other: VarCompatible) -> Self | T_DataArray:
+    def __or__(self, other: VarCompatible) -> Self | T_DA:
         return self._binary_op(other, operator.or_)
 
     @overload
-    def __lshift__(self, other: T_DataArray) -> T_DataArray: ...
+    def __lshift__(self, other: T_DA) -> T_DA: ...
 
     @overload
     def __lshift__(self, other: VarCompatible) -> Self: ...
 
-    def __lshift__(self, other: VarCompatible) -> Self | T_DataArray:
+    def __lshift__(self, other: VarCompatible) -> Self | T_DA:
         return self._binary_op(other, operator.lshift)
 
     @overload
-    def __rshift__(self, other: T_DataArray) -> T_DataArray: ...
+    def __rshift__(self, other: T_DA) -> T_DA: ...
 
     @overload
     def __rshift__(self, other: VarCompatible) -> Self: ...
 
-    def __rshift__(self, other: VarCompatible) -> Self | T_DataArray:
+    def __rshift__(self, other: VarCompatible) -> Self | T_DA:
         return self._binary_op(other, operator.rshift)
 
     @overload
-    def __lt__(self, other: T_DataArray) -> T_DataArray: ...
+    def __lt__(self, other: T_DA) -> T_DA: ...
 
     @overload
     def __lt__(self, other: VarCompatible) -> Self: ...
 
-    def __lt__(self, other: VarCompatible) -> Self | T_DataArray:
+    def __lt__(self, other: VarCompatible) -> Self | T_DA:
         return self._binary_op(other, operator.lt)
 
     @overload
-    def __le__(self, other: T_DataArray) -> T_DataArray: ...
+    def __le__(self, other: T_DA) -> T_DA: ...
 
     @overload
     def __le__(self, other: VarCompatible) -> Self: ...
 
-    def __le__(self, other: VarCompatible) -> Self | T_DataArray:
+    def __le__(self, other: VarCompatible) -> Self | T_DA:
         return self._binary_op(other, operator.le)
 
     @overload
-    def __gt__(self, other: T_DataArray) -> T_DataArray: ...
+    def __gt__(self, other: T_DA) -> T_DA: ...
 
     @overload
     def __gt__(self, other: VarCompatible) -> Self: ...
 
-    def __gt__(self, other: VarCompatible) -> Self | T_DataArray:
+    def __gt__(self, other: VarCompatible) -> Self | T_DA:
         return self._binary_op(other, operator.gt)
 
     @overload
-    def __ge__(self, other: T_DataArray) -> T_DataArray: ...
+    def __ge__(self, other: T_DA) -> T_DA: ...
 
     @overload
     def __ge__(self, other: VarCompatible) -> Self: ...
 
-    def __ge__(self, other: VarCompatible) -> Self | T_DataArray:
+    def __ge__(self, other: VarCompatible) -> Self | T_DA:
         return self._binary_op(other, operator.ge)
 
     @overload  # type:ignore[override]
-    def __eq__(self, other: T_DataArray) -> T_DataArray: ...
+    def __eq__(self, other: T_DA) -> T_DA: ...
 
     @overload
     def __eq__(self, other: VarCompatible) -> Self: ...
 
-    def __eq__(self, other: VarCompatible) -> Self | T_DataArray:
+    def __eq__(self, other: VarCompatible) -> Self | T_DA:
         return self._binary_op(other, nputils.array_eq)
 
     @overload  # type:ignore[override]
-    def __ne__(self, other: T_DataArray) -> T_DataArray: ...
+    def __ne__(self, other: T_DA) -> T_DA: ...
 
     @overload
     def __ne__(self, other: VarCompatible) -> Self: ...
 
-    def __ne__(self, other: VarCompatible) -> Self | T_DataArray:
+    def __ne__(self, other: VarCompatible) -> Self | T_DA:
         return self._binary_op(other, nputils.array_ne)
 
     # When __eq__ is defined but __hash__ is not, then an object is unhashable,
@@ -770,96 +770,96 @@ class DatasetGroupByOpsMixin:
     __slots__ = ()
 
     def _binary_op(
-        self, other: GroupByCompatible, f: Callable, reflexive: bool = False
+        self, other: Dataset | DataArray, f: Callable, reflexive: bool = False
     ) -> Dataset:
         raise NotImplementedError
 
-    def __add__(self, other: GroupByCompatible) -> Dataset:
+    def __add__(self, other: Dataset | DataArray) -> Dataset:
         return self._binary_op(other, operator.add)
 
-    def __sub__(self, other: GroupByCompatible) -> Dataset:
+    def __sub__(self, other: Dataset | DataArray) -> Dataset:
         return self._binary_op(other, operator.sub)
 
-    def __mul__(self, other: GroupByCompatible) -> Dataset:
+    def __mul__(self, other: Dataset | DataArray) -> Dataset:
         return self._binary_op(other, operator.mul)
 
-    def __pow__(self, other: GroupByCompatible) -> Dataset:
+    def __pow__(self, other: Dataset | DataArray) -> Dataset:
         return self._binary_op(other, operator.pow)
 
-    def __truediv__(self, other: GroupByCompatible) -> Dataset:
+    def __truediv__(self, other: Dataset | DataArray) -> Dataset:
         return self._binary_op(other, operator.truediv)
 
-    def __floordiv__(self, other: GroupByCompatible) -> Dataset:
+    def __floordiv__(self, other: Dataset | DataArray) -> Dataset:
         return self._binary_op(other, operator.floordiv)
 
-    def __mod__(self, other: GroupByCompatible) -> Dataset:
+    def __mod__(self, other: Dataset | DataArray) -> Dataset:
         return self._binary_op(other, operator.mod)
 
-    def __and__(self, other: GroupByCompatible) -> Dataset:
+    def __and__(self, other: Dataset | DataArray) -> Dataset:
         return self._binary_op(other, operator.and_)
 
-    def __xor__(self, other: GroupByCompatible) -> Dataset:
+    def __xor__(self, other: Dataset | DataArray) -> Dataset:
         return self._binary_op(other, operator.xor)
 
-    def __or__(self, other: GroupByCompatible) -> Dataset:
+    def __or__(self, other: Dataset | DataArray) -> Dataset:
         return self._binary_op(other, operator.or_)
 
-    def __lshift__(self, other: GroupByCompatible) -> Dataset:
+    def __lshift__(self, other: Dataset | DataArray) -> Dataset:
         return self._binary_op(other, operator.lshift)
 
-    def __rshift__(self, other: GroupByCompatible) -> Dataset:
+    def __rshift__(self, other: Dataset | DataArray) -> Dataset:
         return self._binary_op(other, operator.rshift)
 
-    def __lt__(self, other: GroupByCompatible) -> Dataset:
+    def __lt__(self, other: Dataset | DataArray) -> Dataset:
         return self._binary_op(other, operator.lt)
 
-    def __le__(self, other: GroupByCompatible) -> Dataset:
+    def __le__(self, other: Dataset | DataArray) -> Dataset:
         return self._binary_op(other, operator.le)
 
-    def __gt__(self, other: GroupByCompatible) -> Dataset:
+    def __gt__(self, other: Dataset | DataArray) -> Dataset:
         return self._binary_op(other, operator.gt)
 
-    def __ge__(self, other: GroupByCompatible) -> Dataset:
+    def __ge__(self, other: Dataset | DataArray) -> Dataset:
         return self._binary_op(other, operator.ge)
 
-    def __eq__(self, other: GroupByCompatible) -> Dataset:  # type:ignore[override]
+    def __eq__(self, other: Dataset | DataArray) -> Dataset:  # type:ignore[override]
         return self._binary_op(other, nputils.array_eq)
 
-    def __ne__(self, other: GroupByCompatible) -> Dataset:  # type:ignore[override]
+    def __ne__(self, other: Dataset | DataArray) -> Dataset:  # type:ignore[override]
         return self._binary_op(other, nputils.array_ne)
 
     # When __eq__ is defined but __hash__ is not, then an object is unhashable,
     # and it should be declared as follows:
     __hash__: None  # type:ignore[assignment]
 
-    def __radd__(self, other: GroupByCompatible) -> Dataset:
+    def __radd__(self, other: Dataset | DataArray) -> Dataset:
         return self._binary_op(other, operator.add, reflexive=True)
 
-    def __rsub__(self, other: GroupByCompatible) -> Dataset:
+    def __rsub__(self, other: Dataset | DataArray) -> Dataset:
         return self._binary_op(other, operator.sub, reflexive=True)
 
-    def __rmul__(self, other: GroupByCompatible) -> Dataset:
+    def __rmul__(self, other: Dataset | DataArray) -> Dataset:
         return self._binary_op(other, operator.mul, reflexive=True)
 
-    def __rpow__(self, other: GroupByCompatible) -> Dataset:
+    def __rpow__(self, other: Dataset | DataArray) -> Dataset:
         return self._binary_op(other, operator.pow, reflexive=True)
 
-    def __rtruediv__(self, other: GroupByCompatible) -> Dataset:
+    def __rtruediv__(self, other: Dataset | DataArray) -> Dataset:
         return self._binary_op(other, operator.truediv, reflexive=True)
 
-    def __rfloordiv__(self, other: GroupByCompatible) -> Dataset:
+    def __rfloordiv__(self, other: Dataset | DataArray) -> Dataset:
         return self._binary_op(other, operator.floordiv, reflexive=True)
 
-    def __rmod__(self, other: GroupByCompatible) -> Dataset:
+    def __rmod__(self, other: Dataset | DataArray) -> Dataset:
         return self._binary_op(other, operator.mod, reflexive=True)
 
-    def __rand__(self, other: GroupByCompatible) -> Dataset:
+    def __rand__(self, other: Dataset | DataArray) -> Dataset:
         return self._binary_op(other, operator.and_, reflexive=True)
 
-    def __rxor__(self, other: GroupByCompatible) -> Dataset:
+    def __rxor__(self, other: Dataset | DataArray) -> Dataset:
         return self._binary_op(other, operator.xor, reflexive=True)
 
-    def __ror__(self, other: GroupByCompatible) -> Dataset:
+    def __ror__(self, other: Dataset | DataArray) -> Dataset:
         return self._binary_op(other, operator.or_, reflexive=True)
 
     __add__.__doc__ = operator.add.__doc__
diff --git a/xarray/core/concat.py b/xarray/core/concat.py
index b1cca586992..15292bdb34b 100644
--- a/xarray/core/concat.py
+++ b/xarray/core/concat.py
@@ -32,10 +32,11 @@
     T_DataVars = Union[ConcatOptions, Iterable[Hashable]]
 
 
+# TODO: replace dim: Any by 1D array_likes
 @overload
 def concat(
     objs: Iterable[T_Dataset],
-    dim: Hashable | T_Variable | T_DataArray | pd.Index,
+    dim: Hashable | T_Variable | T_DataArray | pd.Index | Any,
     data_vars: T_DataVars = "all",
     coords: ConcatOptions | list[Hashable] = "different",
     compat: CompatOptions = "equals",
@@ -50,7 +51,7 @@ def concat(
 @overload
 def concat(
     objs: Iterable[T_DataArray],
-    dim: Hashable | T_Variable | T_DataArray | pd.Index,
+    dim: Hashable | T_Variable | T_DataArray | pd.Index | Any,
     data_vars: T_DataVars = "all",
     coords: ConcatOptions | list[Hashable] = "different",
     compat: CompatOptions = "equals",
@@ -303,7 +304,7 @@ def _calc_concat_dim_index(
 
     dim: Hashable | None
 
-    if isinstance(dim_or_data, str):
+    if utils.hashable(dim_or_data):
         dim = dim_or_data
         index = None
     else:
@@ -474,7 +475,7 @@ def _parse_datasets(
 
 
 def _dataset_concat(
-    datasets: list[T_Dataset],
+    datasets: Iterable[T_Dataset],
     dim: str | T_Variable | T_DataArray | pd.Index,
     data_vars: T_DataVars,
     coords: str | list[str],
@@ -505,12 +506,14 @@ def _dataset_concat(
     else:
         dim_var = None
 
-    dim, index = _calc_concat_dim_index(dim)
+    dim_name, index = _calc_concat_dim_index(dim)
 
     # Make sure we're working on a copy (we'll be loading variables)
     datasets = [ds.copy() for ds in datasets]
     datasets = list(
-        align(*datasets, join=join, copy=False, exclude=[dim], fill_value=fill_value)
+        align(
+            *datasets, join=join, copy=False, exclude=[dim_name], fill_value=fill_value
+        )
     )
 
     dim_coords, dims_sizes, coord_names, data_names, vars_order = _parse_datasets(
@@ -524,19 +527,21 @@ def _dataset_concat(
             f"{both_data_and_coords!r} is a coordinate in some datasets but not others."
         )
     # we don't want the concat dimension in the result dataset yet
-    dim_coords.pop(dim, None)
-    dims_sizes.pop(dim, None)
+    dim_coords.pop(dim_name, None)
+    dims_sizes.pop(dim_name, None)
 
     # case where concat dimension is a coordinate or data_var but not a dimension
-    if (dim in coord_names or dim in data_names) and dim not in dim_names:
+    if (
+        dim_name in coord_names or dim_name in data_names
+    ) and dim_name not in dim_names:
         datasets = [
-            ds.expand_dims(dim, create_index_for_new_dim=create_index_for_new_dim)
+            ds.expand_dims(dim_name, create_index_for_new_dim=create_index_for_new_dim)
             for ds in datasets
         ]
 
     # determine which variables to concatenate
     concat_over, equals, concat_dim_lengths = _calc_concat_over(
-        datasets, dim, dim_names, data_vars, coords, compat
+        datasets, dim_name, dim_names, data_vars, coords, compat
     )
 
     # determine which variables to merge, and then merge them according to compat
@@ -576,8 +581,8 @@ def ensure_common_dims(vars, concat_dim_lengths):
         # dimensions and the same shape for all of them except along the
         # concat dimension
         common_dims = tuple(utils.OrderedSet(d for v in vars for d in v.dims))
-        if dim not in common_dims:
-            common_dims = (dim,) + common_dims
+        if dim_name not in common_dims:
+            common_dims = (dim_name,) + common_dims
         for var, dim_len in zip(vars, concat_dim_lengths):
             if var.dims != common_dims:
                 common_shape = tuple(dims_sizes.get(d, dim_len) for d in common_dims)
@@ -593,12 +598,12 @@ def get_indexes(name):
         for ds in datasets:
             if name in ds._indexes:
                 yield ds._indexes[name]
-            elif name == dim:
+            elif name == dim_name:
                 var = ds._variables[name]
                 if not var.dims:
-                    data = var.set_dims(dim).values
+                    data = var.set_dims(dim_name).values
                     if create_index_for_new_dim:
-                        yield PandasIndex(data, dim, coord_dtype=var.dtype)
+                        yield PandasIndex(data, dim_name, coord_dtype=var.dtype)
 
     # create concatenation index, needed for later reindexing
     file_start_indexes = np.append(0, np.cumsum(concat_dim_lengths))
@@ -644,7 +649,7 @@ def get_indexes(name):
                         f"{name!r} must have either an index or no index in all datasets, "
                         f"found {len(indexes)}/{len(datasets)} datasets with an index."
                     )
-                combined_idx = indexes[0].concat(indexes, dim, positions)
+                combined_idx = indexes[0].concat(indexes, dim_name, positions)
                 if name in datasets[0]._indexes:
                     idx_vars = datasets[0].xindexes.get_all_coords(name)
                 else:
@@ -660,14 +665,14 @@ def get_indexes(name):
                     result_vars[k] = v
             else:
                 combined_var = concat_vars(
-                    vars, dim, positions, combine_attrs=combine_attrs
+                    vars, dim_name, positions, combine_attrs=combine_attrs
                 )
                 # reindex if variable is not present in all datasets
                 if len(variable_index) < concat_index_size:
                     combined_var = reindex_variables(
                         variables={name: combined_var},
                         dim_pos_indexers={
-                            dim: pd.Index(variable_index).get_indexer(concat_index)
+                            dim_name: pd.Index(variable_index).get_indexer(concat_index)
                         },
                         fill_value=fill_value,
                     )[name]
@@ -693,12 +698,12 @@ def get_indexes(name):
 
     if index is not None:
         if dim_var is not None:
-            index_vars = index.create_variables({dim: dim_var})
+            index_vars = index.create_variables({dim_name: dim_var})
         else:
             index_vars = index.create_variables()
 
-        coord_vars[dim] = index_vars[dim]
-        result_indexes[dim] = index
+        coord_vars[dim_name] = index_vars[dim_name]
+        result_indexes[dim_name] = index
 
     coords_obj = Coordinates(coord_vars, indexes=result_indexes)
 
diff --git a/xarray/core/dataarray.py b/xarray/core/dataarray.py
index 47dc9d13ffc..09f5664aa06 100644
--- a/xarray/core/dataarray.py
+++ b/xarray/core/dataarray.py
@@ -135,7 +135,11 @@ def _check_coords_dims(shape, coords, dim):
 
 def _infer_coords_and_dims(
     shape: tuple[int, ...],
-    coords: Sequence[Sequence | pd.Index | DataArray] | Mapping | None,
+    coords: (
+        Sequence[Sequence | pd.Index | DataArray | Variable | np.ndarray]
+        | Mapping
+        | None
+    ),
     dims: str | Iterable[Hashable] | None,
 ) -> tuple[Mapping[Hashable, Any], tuple[Hashable, ...]]:
     """All the logic for creating a new DataArray"""
@@ -199,7 +203,11 @@ def _infer_coords_and_dims(
 
 def _check_data_shape(
     data: Any,
-    coords: Sequence[Sequence | pd.Index | DataArray] | Mapping | None,
+    coords: (
+        Sequence[Sequence | pd.Index | DataArray | Variable | np.ndarray]
+        | Mapping
+        | None
+    ),
     dims: str | Iterable[Hashable] | None,
 ) -> Any:
     if data is dtypes.NA:
@@ -413,7 +421,11 @@ class DataArray(
     def __init__(
         self,
         data: Any = dtypes.NA,
-        coords: Sequence[Sequence | pd.Index | DataArray] | Mapping | None = None,
+        coords: (
+            Sequence[Sequence | pd.Index | DataArray | Variable | np.ndarray]
+            | Mapping
+            | None
+        ) = None,
         dims: str | Iterable[Hashable] | None = None,
         name: Hashable | None = None,
         attrs: Mapping | None = None,
@@ -965,7 +977,7 @@ def indexes(self) -> Indexes:
         return self.xindexes.to_pandas_indexes()
 
     @property
-    def xindexes(self) -> Indexes:
+    def xindexes(self) -> Indexes[Index]:
         """Mapping of :py:class:`~xarray.indexes.Index` objects
         used for label based indexing.
         """
@@ -3004,7 +3016,7 @@ def to_unstacked_dataset(self, dim: Hashable, level: int | Hashable = 0) -> Data
         if not isinstance(idx, pd.MultiIndex):
             raise ValueError(f"'{dim}' is not a stacked coordinate")
 
-        level_number = idx._get_level_number(level)
+        level_number = idx._get_level_number(level)  # type: ignore[attr-defined]
         variables = idx.levels[level_number]
         variable_dim = idx.names[level_number]
 
@@ -3838,7 +3850,7 @@ def to_pandas(self) -> Self | pd.Series | pd.DataFrame:
                 "pandas objects. Requires 2 or fewer dimensions."
             )
         indexes = [self.get_index(dim) for dim in self.dims]
-        return constructor(self.values, *indexes)
+        return constructor(self.values, *indexes)  # type: ignore[operator]
 
     def to_dataframe(
         self, name: Hashable | None = None, dim_order: Sequence[Hashable] | None = None
@@ -6841,7 +6853,7 @@ def groupby_bins(
 
         _validate_groupby_squeeze(squeeze)
         grouper = BinGrouper(
-            bins=bins,
+            bins=bins,  # type: ignore[arg-type]  # TODO: fix this arg or BinGrouper
             cut_kwargs={
                 "right": right,
                 "labels": labels,
diff --git a/xarray/core/dataset.py b/xarray/core/dataset.py
index 3930b12ef3d..1793abf02d8 100644
--- a/xarray/core/dataset.py
+++ b/xarray/core/dataset.py
@@ -4156,15 +4156,15 @@ def interp_like(
             kwargs = {}
 
         # pick only dimension coordinates with a single index
-        coords = {}
+        coords: dict[Hashable, Variable] = {}
         other_indexes = other.xindexes
         for dim in self.dims:
             other_dim_coords = other_indexes.get_all_coords(dim, errors="ignore")
             if len(other_dim_coords) == 1:
                 coords[dim] = other_dim_coords[dim]
 
-        numeric_coords: dict[Hashable, pd.Index] = {}
-        object_coords: dict[Hashable, pd.Index] = {}
+        numeric_coords: dict[Hashable, Variable] = {}
+        object_coords: dict[Hashable, Variable] = {}
         for k, v in coords.items():
             if v.dtype.kind in "uifcMm":
                 numeric_coords[k] = v
@@ -6539,7 +6539,13 @@ def interpolate_na(
         limit: int | None = None,
         use_coordinate: bool | Hashable = True,
         max_gap: (
-            int | float | str | pd.Timedelta | np.timedelta64 | datetime.timedelta
+            int
+            | float
+            | str
+            | pd.Timedelta
+            | np.timedelta64
+            | datetime.timedelta
+            | None
         ) = None,
         **kwargs: Any,
     ) -> Self:
@@ -6573,7 +6579,8 @@ def interpolate_na(
             or None for no limit. This filling is done regardless of the size of
             the gap in the data. To only interpolate over gaps less than a given length,
             see ``max_gap``.
-        max_gap : int, float, str, pandas.Timedelta, numpy.timedelta64, datetime.timedelta, default: None
+        max_gap : int, float, str, pandas.Timedelta, numpy.timedelta64, datetime.timedelta \
+            or None, default: None
             Maximum size of gap, a continuous sequence of NaNs, that will be filled.
             Use None for no limit. When interpolating along a datetime64 dimension
             and ``use_coordinate=True``, ``max_gap`` can be one of the following:
@@ -9715,7 +9722,7 @@ def eval(
             c        (x) float64 40B 0.0 1.25 2.5 3.75 5.0
         """
 
-        return pd.eval(
+        return pd.eval(  # type: ignore[return-value]
             statement,
             resolvers=[self],
             target=self,
@@ -10394,7 +10401,7 @@ def groupby_bins(
 
         _validate_groupby_squeeze(squeeze)
         grouper = BinGrouper(
-            bins=bins,
+            bins=bins,  # type: ignore[arg-type]  #TODO: fix this here or in BinGrouper?
             cut_kwargs={
                 "right": right,
                 "labels": labels,
diff --git a/xarray/core/extension_array.py b/xarray/core/extension_array.py
index c8b4fa88409..b0361ef0f0f 100644
--- a/xarray/core/extension_array.py
+++ b/xarray/core/extension_array.py
@@ -1,7 +1,7 @@
 from __future__ import annotations
 
 from collections.abc import Sequence
-from typing import Callable, Generic
+from typing import Callable, Generic, cast
 
 import numpy as np
 import pandas as pd
@@ -45,7 +45,7 @@ def __extension_duck_array__stack(arr: T_ExtensionArray, axis: int):
 def __extension_duck_array__concatenate(
     arrays: Sequence[T_ExtensionArray], axis: int = 0, out=None
 ) -> T_ExtensionArray:
-    return type(arrays[0])._concat_same_type(arrays)
+    return type(arrays[0])._concat_same_type(arrays)  # type: ignore[attr-defined]
 
 
 @implements(np.where)
@@ -57,9 +57,9 @@ def __extension_duck_array__where(
         and isinstance(y, pd.Categorical)
         and x.dtype != y.dtype
     ):
-        x = x.add_categories(set(y.categories).difference(set(x.categories)))
-        y = y.add_categories(set(x.categories).difference(set(y.categories)))
-    return pd.Series(x).where(condition, pd.Series(y)).array
+        x = x.add_categories(set(y.categories).difference(set(x.categories)))  # type: ignore[assignment]
+        y = y.add_categories(set(x.categories).difference(set(y.categories)))  # type: ignore[assignment]
+    return cast(T_ExtensionArray, pd.Series(x).where(condition, pd.Series(y)).array)
 
 
 class PandasExtensionArray(Generic[T_ExtensionArray]):
@@ -116,7 +116,7 @@ def __getitem__(self, key) -> PandasExtensionArray[T_ExtensionArray]:
         if is_extension_array_dtype(item):
             return type(self)(item)
         if np.isscalar(item):
-            return type(self)(type(self.array)([item]))
+            return type(self)(type(self.array)([item]))  # type: ignore[call-arg]  # only subclasses with proper __init__ allowed
         return item
 
     def __setitem__(self, key, val):
diff --git a/xarray/core/groupers.py b/xarray/core/groupers.py
index 075afd9f62f..f76bd22a2f6 100644
--- a/xarray/core/groupers.py
+++ b/xarray/core/groupers.py
@@ -10,7 +10,7 @@
 from abc import ABC, abstractmethod
 from collections.abc import Mapping, Sequence
 from dataclasses import dataclass, field
-from typing import Any
+from typing import TYPE_CHECKING, Any, cast
 
 import numpy as np
 import pandas as pd
@@ -25,6 +25,9 @@
 from xarray.core.utils import emit_user_level_warning
 from xarray.core.variable import Variable
 
+if TYPE_CHECKING:
+    pass
+
 __all__ = [
     "EncodedGroups",
     "Grouper",
@@ -160,6 +163,7 @@ def _factorize_dummy(self) -> EncodedGroups:
         # equivalent to: group_indices = group_indices.reshape(-1, 1)
         group_indices: T_GroupIndices = [slice(i, i + 1) for i in range(size)]
         size_range = np.arange(size)
+        full_index: pd.Index
         if isinstance(self.group, _DummyGroup):
             codes = self.group.to_dataarray().copy(data=size_range)
             unique_coord = self.group
@@ -275,7 +279,7 @@ def _init_properties(self, group: T_Group) -> None:
         if isinstance(group_as_index, CFTimeIndex):
             from xarray.core.resample_cftime import CFTimeGrouper
 
-            index_grouper = CFTimeGrouper(
+            self.index_grouper = CFTimeGrouper(
                 freq=self.freq,
                 closed=self.closed,
                 label=self.label,
@@ -284,7 +288,7 @@ def _init_properties(self, group: T_Group) -> None:
                 loffset=self.loffset,
             )
         else:
-            index_grouper = pd.Grouper(
+            self.index_grouper = pd.Grouper(
                 # TODO remove once requiring pandas >= 2.2
                 freq=_new_to_legacy_freq(self.freq),
                 closed=self.closed,
@@ -292,7 +296,6 @@ def _init_properties(self, group: T_Group) -> None:
                 origin=self.origin,
                 offset=offset,
             )
-        self.index_grouper = index_grouper
         self.group_as_index = group_as_index
 
     def _get_index_and_items(self) -> tuple[pd.Index, pd.Series, np.ndarray]:
@@ -305,22 +308,25 @@ def _get_index_and_items(self) -> tuple[pd.Index, pd.Series, np.ndarray]:
         return full_index, first_items, codes
 
     def first_items(self) -> tuple[pd.Series, np.ndarray]:
-        from xarray import CFTimeIndex
+        from xarray.coding.cftimeindex import CFTimeIndex
+        from xarray.core.resample_cftime import CFTimeGrouper
 
-        if isinstance(self.group_as_index, CFTimeIndex):
-            return self.index_grouper.first_items(self.group_as_index)
-        else:
-            s = pd.Series(np.arange(self.group_as_index.size), self.group_as_index)
-            grouped = s.groupby(self.index_grouper)
-            first_items = grouped.first()
-            counts = grouped.count()
-            # This way we generate codes for the final output index: full_index.
-            # So for _flox_reduce we avoid one reindex and copy by avoiding
-            # _maybe_restore_empty_groups
-            codes = np.repeat(np.arange(len(first_items)), counts)
-            if self.loffset is not None:
-                _apply_loffset(self.loffset, first_items)
-            return first_items, codes
+        if isinstance(self.index_grouper, CFTimeGrouper):
+            return self.index_grouper.first_items(
+                cast(CFTimeIndex, self.group_as_index)
+            )
+
+        s = pd.Series(np.arange(self.group_as_index.size), self.group_as_index)
+        grouped = s.groupby(self.index_grouper)
+        first_items = grouped.first()
+        counts = grouped.count()
+        # This way we generate codes for the final output index: full_index.
+        # So for _flox_reduce we avoid one reindex and copy by avoiding
+        # _maybe_restore_empty_groups
+        codes = np.repeat(np.arange(len(first_items)), counts)
+        if self.loffset is not None:
+            _apply_loffset(self.loffset, first_items)
+        return first_items, codes
 
     def factorize(self, group) -> EncodedGroups:
         self._init_properties(group)
@@ -369,7 +375,7 @@ def _apply_loffset(
         )
 
     if isinstance(loffset, str):
-        loffset = pd.tseries.frequencies.to_offset(loffset)
+        loffset = pd.tseries.frequencies.to_offset(loffset)  # type: ignore[assignment]
 
     needs_offset = (
         isinstance(loffset, (pd.DateOffset, datetime.timedelta))
diff --git a/xarray/core/indexes.py b/xarray/core/indexes.py
index f25c0ecf936..9d8a68edbf3 100644
--- a/xarray/core/indexes.py
+++ b/xarray/core/indexes.py
@@ -451,7 +451,7 @@ def safe_cast_to_index(array: Any) -> pd.Index:
     elif isinstance(array, PandasIndexingAdapter):
         index = array.array
     else:
-        kwargs: dict[str, str] = {}
+        kwargs: dict[str, Any] = {}
         if hasattr(array, "dtype"):
             if array.dtype.kind == "O":
                 kwargs["dtype"] = "object"
@@ -551,7 +551,7 @@ def as_scalar(value: np.ndarray):
     return value[()] if value.dtype.kind in "mM" else value.item()
 
 
-def get_indexer_nd(index, labels, method=None, tolerance=None):
+def get_indexer_nd(index: pd.Index, labels, method=None, tolerance=None) -> np.ndarray:
     """Wrapper around :meth:`pandas.Index.get_indexer` supporting n-dimensional
     labels
     """
@@ -740,7 +740,7 @@ def isel(
             # scalar indexer: drop index
             return None
 
-        return self._replace(self.index[indxr])
+        return self._replace(self.index[indxr])  # type: ignore[index]
 
     def sel(
         self, labels: dict[Any, Any], method=None, tolerance=None
@@ -898,36 +898,45 @@ def _check_dim_compat(variables: Mapping[Any, Variable], all_dims: str = "equal"
         )
 
 
-def remove_unused_levels_categories(index: pd.Index) -> pd.Index:
+T_PDIndex = TypeVar("T_PDIndex", bound=pd.Index)
+
+
+def remove_unused_levels_categories(index: T_PDIndex) -> T_PDIndex:
     """
     Remove unused levels from MultiIndex and unused categories from CategoricalIndex
     """
     if isinstance(index, pd.MultiIndex):
-        index = index.remove_unused_levels()
+        new_index = cast(pd.MultiIndex, index.remove_unused_levels())
         # if it contains CategoricalIndex, we need to remove unused categories
         # manually. See https://github.com/pandas-dev/pandas/issues/30846
-        if any(isinstance(lev, pd.CategoricalIndex) for lev in index.levels):
+        if any(isinstance(lev, pd.CategoricalIndex) for lev in new_index.levels):
             levels = []
-            for i, level in enumerate(index.levels):
+            for i, level in enumerate(new_index.levels):
                 if isinstance(level, pd.CategoricalIndex):
-                    level = level[index.codes[i]].remove_unused_categories()
+                    level = level[new_index.codes[i]].remove_unused_categories()
                 else:
-                    level = level[index.codes[i]]
+                    level = level[new_index.codes[i]]
                 levels.append(level)
             # TODO: calling from_array() reorders MultiIndex levels. It would
             # be best to avoid this, if possible, e.g., by using
             # MultiIndex.remove_unused_levels() (which does not reorder) on the
             # part of the MultiIndex that is not categorical, or by fixing this
             # upstream in pandas.
-            index = pd.MultiIndex.from_arrays(levels, names=index.names)
-    elif isinstance(index, pd.CategoricalIndex):
-        index = index.remove_unused_categories()
+            new_index = pd.MultiIndex.from_arrays(levels, names=new_index.names)
+        return cast(T_PDIndex, new_index)
+
+    if isinstance(index, pd.CategoricalIndex):
+        return index.remove_unused_categories()  # type: ignore[attr-defined]
+
     return index
 
 
 class PandasMultiIndex(PandasIndex):
     """Wrap a pandas.MultiIndex as an xarray compatible index."""
 
+    index: pd.MultiIndex
+    dim: Hashable
+    coord_dtype: Any
     level_coords_dtype: dict[str, Any]
 
     __slots__ = ("index", "dim", "coord_dtype", "level_coords_dtype")
@@ -1063,8 +1072,8 @@ def from_variables_maybe_expand(
         The index and its corresponding coordinates may be created along a new dimension.
         """
         names: list[Hashable] = []
-        codes: list[list[int]] = []
-        levels: list[list[int]] = []
+        codes: list[Iterable[int]] = []
+        levels: list[Iterable[Any]] = []
         level_variables: dict[Any, Variable] = {}
 
         _check_dim_compat({**current_variables, **variables})
@@ -1134,7 +1143,7 @@ def reorder_levels(
         its corresponding coordinates.
 
         """
-        index = self.index.reorder_levels(level_variables.keys())
+        index = cast(pd.MultiIndex, self.index.reorder_levels(level_variables.keys()))
         level_coords_dtype = {k: self.level_coords_dtype[k] for k in index.names}
         return self._replace(index, level_coords_dtype=level_coords_dtype)
 
@@ -1147,13 +1156,13 @@ def create_variables(
             variables = {}
 
         index_vars: IndexVars = {}
-        for name in (self.dim,) + self.index.names:
+        for name in (self.dim,) + tuple(self.index.names):
             if name == self.dim:
                 level = None
                 dtype = None
             else:
                 level = name
-                dtype = self.level_coords_dtype[name]
+                dtype = self.level_coords_dtype[name]  # type: ignore[index]  # TODO: are Hashables ok?
 
             var = variables.get(name, None)
             if var is not None:
@@ -1163,7 +1172,7 @@ def create_variables(
                 attrs = {}
                 encoding = {}
 
-            data = PandasMultiIndexingAdapter(self.index, dtype=dtype, level=level)
+            data = PandasMultiIndexingAdapter(self.index, dtype=dtype, level=level)  # type: ignore[arg-type]  # TODO: are Hashables ok?
             index_vars[name] = IndexVariable(
                 self.dim,
                 data,
@@ -1186,6 +1195,8 @@ def sel(self, labels, method=None, tolerance=None) -> IndexSelResult:
         new_index = None
         scalar_coord_values = {}
 
+        indexer: int | slice | np.ndarray | Variable | DataArray
+
         # label(s) given for multi-index level(s)
         if all([lbl in self.index.names for lbl in labels]):
             label_values = {}
@@ -1212,7 +1223,7 @@ def sel(self, labels, method=None, tolerance=None) -> IndexSelResult:
                 )
                 scalar_coord_values.update(label_values)
                 # GH2619. Raise a KeyError if nothing is chosen
-                if indexer.dtype.kind == "b" and indexer.sum() == 0:
+                if indexer.dtype.kind == "b" and indexer.sum() == 0:  # type: ignore[union-attr]
                     raise KeyError(f"{labels} not found")
 
         # assume one label value given for the multi-index "array" (dimension)
@@ -1600,9 +1611,7 @@ def group_by_index(
         """Returns a list of unique indexes and their corresponding coordinates."""
 
         index_coords = []
-
-        for i in self._id_index:
-            index = self._id_index[i]
+        for i, index in self._id_index.items():
             coords = {k: self._variables[k] for k in self._id_coord_names[i]}
             index_coords.append((index, coords))
 
@@ -1640,26 +1649,28 @@ def copy_indexes(
             in this dict.
 
         """
-        new_indexes = {}
-        new_index_vars = {}
+        new_indexes: dict[Hashable, T_PandasOrXarrayIndex] = {}
+        new_index_vars: dict[Hashable, Variable] = {}
 
-        idx: T_PandasOrXarrayIndex
+        xr_idx: Index
+        new_idx: T_PandasOrXarrayIndex
         for idx, coords in self.group_by_index():
             if isinstance(idx, pd.Index):
                 convert_new_idx = True
                 dim = next(iter(coords.values())).dims[0]
                 if isinstance(idx, pd.MultiIndex):
-                    idx = PandasMultiIndex(idx, dim)
+                    xr_idx = PandasMultiIndex(idx, dim)
                 else:
-                    idx = PandasIndex(idx, dim)
+                    xr_idx = PandasIndex(idx, dim)
             else:
                 convert_new_idx = False
+                xr_idx = idx
 
-            new_idx = idx._copy(deep=deep, memo=memo)
-            idx_vars = idx.create_variables(coords)
+            new_idx = xr_idx._copy(deep=deep, memo=memo)  # type: ignore[assignment]
+            idx_vars = xr_idx.create_variables(coords)
 
             if convert_new_idx:
-                new_idx = cast(PandasIndex, new_idx).index
+                new_idx = new_idx.index  # type: ignore[attr-defined]
 
             new_indexes.update({k: new_idx for k in coords})
             new_index_vars.update(idx_vars)
diff --git a/xarray/core/indexing.py b/xarray/core/indexing.py
index 06e7efdbb48..19937270268 100644
--- a/xarray/core/indexing.py
+++ b/xarray/core/indexing.py
@@ -34,6 +34,7 @@
     from numpy.typing import DTypeLike
 
     from xarray.core.indexes import Index
+    from xarray.core.types import Self
     from xarray.core.variable import Variable
     from xarray.namedarray._typing import _Shape, duckarray
     from xarray.namedarray.parallelcompat import ChunkManagerEntrypoint
@@ -1656,6 +1657,9 @@ class PandasIndexingAdapter(ExplicitlyIndexedNDArrayMixin):
 
     __slots__ = ("array", "_dtype")
 
+    array: pd.Index
+    _dtype: np.dtype
+
     def __init__(self, array: pd.Index, dtype: DTypeLike = None):
         from xarray.core.indexes import safe_cast_to_index
 
@@ -1792,7 +1796,7 @@ def transpose(self, order) -> pd.Index:
     def __repr__(self) -> str:
         return f"{type(self).__name__}(array={self.array!r}, dtype={self.dtype!r})"
 
-    def copy(self, deep: bool = True) -> PandasIndexingAdapter:
+    def copy(self, deep: bool = True) -> Self:
         # Not the same as just writing `self.array.copy(deep=deep)`, as
         # shallow copies of the underlying numpy.ndarrays become deep ones
         # upon pickling
@@ -1810,11 +1814,14 @@ class PandasMultiIndexingAdapter(PandasIndexingAdapter):
     This allows creating one instance for each multi-index level while
     preserving indexing efficiency (memoized + might reuse another instance with
     the same multi-index).
-
     """
 
     __slots__ = ("array", "_dtype", "level", "adapter")
 
+    array: pd.MultiIndex
+    _dtype: np.dtype
+    level: str | None
+
     def __init__(
         self,
         array: pd.MultiIndex,
@@ -1910,7 +1917,7 @@ def _repr_html_(self) -> str:
         array_repr = short_array_repr(self._get_array_subset())
         return f"<pre>{escape(array_repr)}</pre>"
 
-    def copy(self, deep: bool = True) -> PandasMultiIndexingAdapter:
+    def copy(self, deep: bool = True) -> Self:
         # see PandasIndexingAdapter.copy
         array = self.array.copy(deep=True) if deep else self.array
         return type(self)(array, self._dtype, self.level)
diff --git a/xarray/core/missing.py b/xarray/core/missing.py
index 45abc70c0d3..bfbad72649a 100644
--- a/xarray/core/missing.py
+++ b/xarray/core/missing.py
@@ -315,7 +315,9 @@ def interp_na(
     use_coordinate: bool | str = True,
     method: InterpOptions = "linear",
     limit: int | None = None,
-    max_gap: int | float | str | pd.Timedelta | np.timedelta64 | dt.timedelta = None,
+    max_gap: (
+        int | float | str | pd.Timedelta | np.timedelta64 | dt.timedelta | None
+    ) = None,
     keep_attrs: bool | None = None,
     **kwargs,
 ):
diff --git a/xarray/core/resample_cftime.py b/xarray/core/resample_cftime.py
index 216bd8fca6b..a048e85b4d4 100644
--- a/xarray/core/resample_cftime.py
+++ b/xarray/core/resample_cftime.py
@@ -66,6 +66,13 @@ class CFTimeGrouper:
     single method, the only one required for resampling in xarray.  It cannot
     be used in a call to groupby like a pandas.Grouper object can."""
 
+    freq: BaseCFTimeOffset
+    closed: SideOptions
+    label: SideOptions
+    loffset: str | datetime.timedelta | BaseCFTimeOffset | None
+    origin: str | CFTimeDatetime
+    offset: datetime.timedelta | None
+
     def __init__(
         self,
         freq: str | BaseCFTimeOffset,
@@ -73,11 +80,8 @@ def __init__(
         label: SideOptions | None = None,
         loffset: str | datetime.timedelta | BaseCFTimeOffset | None = None,
         origin: str | CFTimeDatetime = "start_day",
-        offset: str | datetime.timedelta | None = None,
+        offset: str | datetime.timedelta | BaseCFTimeOffset | None = None,
     ):
-        self.offset: datetime.timedelta | None
-        self.closed: SideOptions
-        self.label: SideOptions
         self.freq = to_offset(freq)
         self.loffset = loffset
         self.origin = origin
@@ -120,10 +124,10 @@ def __init__(
         if offset is not None:
             try:
                 self.offset = _convert_offset_to_timedelta(offset)
-            except (ValueError, AttributeError) as error:
+            except (ValueError, TypeError) as error:
                 raise ValueError(
                     f"offset must be a datetime.timedelta object or an offset string "
-                    f"that can be converted to a timedelta.  Got {offset} instead."
+                    f"that can be converted to a timedelta. Got {type(offset)} instead."
                 ) from error
         else:
             self.offset = None
@@ -250,12 +254,12 @@ def _get_time_bins(
 
 
 def _adjust_bin_edges(
-    datetime_bins: np.ndarray,
+    datetime_bins: CFTimeIndex,
     freq: BaseCFTimeOffset,
     closed: SideOptions,
     index: CFTimeIndex,
-    labels: np.ndarray,
-):
+    labels: CFTimeIndex,
+) -> tuple[CFTimeIndex, CFTimeIndex]:
     """This is required for determining the bin edges resampling with
     month end, quarter end, and year end frequencies.
 
@@ -499,10 +503,11 @@ def _convert_offset_to_timedelta(
 ) -> datetime.timedelta:
     if isinstance(offset, datetime.timedelta):
         return offset
-    elif isinstance(offset, (str, Tick)):
-        return to_offset(offset).as_timedelta()
-    else:
-        raise ValueError
+    if isinstance(offset, (str, Tick)):
+        timedelta_cftime_offset = to_offset(offset)
+        if isinstance(timedelta_cftime_offset, Tick):
+            return timedelta_cftime_offset.as_timedelta()
+    raise TypeError(f"Expected timedelta, str or Tick, got {type(offset)}")
 
 
 def _ceil_via_cftimeindex(date: CFTimeDatetime, freq: str | BaseCFTimeOffset):
diff --git a/xarray/core/types.py b/xarray/core/types.py
index 588d15dc35d..786ab5973b1 100644
--- a/xarray/core/types.py
+++ b/xarray/core/types.py
@@ -28,10 +28,11 @@
     else:
         Self: Any = None
 
-if TYPE_CHECKING:
-    from numpy._typing import _SupportsDType
-    from numpy.typing import ArrayLike
 
+from numpy._typing import _SupportsDType
+from numpy.typing import ArrayLike
+
+if TYPE_CHECKING:
     from xarray.backends.common import BackendEntrypoint
     from xarray.core.alignment import Aligner
     from xarray.core.common import AbstractArray, DataWithCoords
@@ -45,7 +46,7 @@
     try:
         from dask.array import Array as DaskArray
     except ImportError:
-        DaskArray = np.ndarray  # type: ignore
+        DaskArray = np.ndarray
 
     try:
         from cubed import Array as CubedArray
@@ -177,7 +178,7 @@ def copy(
 T_ExtensionArray = TypeVar("T_ExtensionArray", bound=pd.api.extensions.ExtensionArray)
 
 
-ScalarOrArray = Union["ArrayLike", np.generic, np.ndarray, "DaskArray"]
+ScalarOrArray = Union["ArrayLike", np.generic]
 VarCompatible = Union["Variable", "ScalarOrArray"]
 DaCompatible = Union["DataArray", "VarCompatible"]
 DsCompatible = Union["Dataset", "DaCompatible"]
@@ -219,6 +220,7 @@ def copy(
 DatetimeUnitOptions = Literal[
     "Y", "M", "W", "D", "h", "m", "s", "ms", "us", "μs", "ns", "ps", "fs", "as", None
 ]
+NPDatetimeUnitOptions = Literal["D", "h", "m", "s", "ms", "us", "ns"]
 
 QueryEngineOptions = Literal["python", "numexpr", None]
 QueryParserOptions = Literal["pandas", "python"]
diff --git a/xarray/core/utils.py b/xarray/core/utils.py
index 5cb52cbd25c..c2859632360 100644
--- a/xarray/core/utils.py
+++ b/xarray/core/utils.py
@@ -57,19 +57,12 @@
     Mapping,
     MutableMapping,
     MutableSet,
+    Sequence,
     ValuesView,
 )
 from enum import Enum
 from pathlib import Path
-from typing import (
-    TYPE_CHECKING,
-    Any,
-    Callable,
-    Generic,
-    Literal,
-    TypeVar,
-    overload,
-)
+from typing import TYPE_CHECKING, Any, Callable, Generic, Literal, TypeVar, overload
 
 import numpy as np
 import pandas as pd
@@ -117,26 +110,27 @@ def wrapper(*args, **kwargs):
     return wrapper
 
 
-def get_valid_numpy_dtype(array: np.ndarray | pd.Index):
+def get_valid_numpy_dtype(array: np.ndarray | pd.Index) -> np.dtype:
     """Return a numpy compatible dtype from either
     a numpy array or a pandas.Index.
 
-    Used for wrapping a pandas.Index as an xarray,Variable.
+    Used for wrapping a pandas.Index as an xarray.Variable.
 
     """
     if isinstance(array, pd.PeriodIndex):
-        dtype = np.dtype("O")
-    elif hasattr(array, "categories"):
+        return np.dtype("O")
+
+    if hasattr(array, "categories"):
         # category isn't a real numpy dtype
         dtype = array.categories.dtype
         if not is_valid_numpy_dtype(dtype):
             dtype = np.dtype("O")
-    elif not is_valid_numpy_dtype(array.dtype):
-        dtype = np.dtype("O")
-    else:
-        dtype = array.dtype
+        return dtype
+
+    if not is_valid_numpy_dtype(array.dtype):
+        return np.dtype("O")
 
-    return dtype
+    return array.dtype  # type: ignore[return-value]
 
 
 def maybe_coerce_to_str(index, original_coords):
@@ -183,18 +177,17 @@ def equivalent(first: T, second: T) -> bool:
     if isinstance(first, np.ndarray) or isinstance(second, np.ndarray):
         return duck_array_ops.array_equiv(first, second)
     if isinstance(first, list) or isinstance(second, list):
-        return list_equiv(first, second)
-    return (first == second) or (pd.isnull(first) and pd.isnull(second))
+        return list_equiv(first, second)  # type: ignore[arg-type]
+    return (first == second) or (pd.isnull(first) and pd.isnull(second))  # type: ignore[call-overload]
 
 
-def list_equiv(first, second):
-    equiv = True
+def list_equiv(first: Sequence[T], second: Sequence[T]) -> bool:
     if len(first) != len(second):
         return False
-    else:
-        for f, s in zip(first, second):
-            equiv = equiv and equivalent(f, s)
-    return equiv
+    for f, s in zip(first, second):
+        if not equivalent(f, s):
+            return False
+    return True
 
 
 def peek_at(iterable: Iterable[T]) -> tuple[T, Iterator[T]]:
diff --git a/xarray/core/variable.py b/xarray/core/variable.py
index f0685882595..377dafa6f79 100644
--- a/xarray/core/variable.py
+++ b/xarray/core/variable.py
@@ -298,7 +298,7 @@ def as_compatible_data(
 
     # we don't want nested self-described arrays
     if isinstance(data, (pd.Series, pd.DataFrame)):
-        data = data.values
+        data = data.values  # type: ignore[assignment]
 
     if isinstance(data, np.ma.MaskedArray):
         mask = np.ma.getmaskarray(data)
@@ -1504,7 +1504,7 @@ def _unstack_once(
         # Potentially we could replace `len(other_dims)` with just `-1`
         other_dims = [d for d in self.dims if d != dim]
         new_shape = tuple(list(reordered.shape[: len(other_dims)]) + new_dim_sizes)
-        new_dims = reordered.dims[: len(other_dims)] + new_dim_names
+        new_dims = reordered.dims[: len(other_dims)] + tuple(new_dim_names)
 
         create_template: Callable
         if fill_value is dtypes.NA:
diff --git a/xarray/namedarray/daskmanager.py b/xarray/namedarray/daskmanager.py
index 14744d2de6b..963d12fd865 100644
--- a/xarray/namedarray/daskmanager.py
+++ b/xarray/namedarray/daskmanager.py
@@ -21,13 +21,13 @@
     try:
         from dask.array import Array as DaskArray
     except ImportError:
-        DaskArray = np.ndarray[Any, Any]  # type: ignore[assignment,  misc]
+        DaskArray = np.ndarray[Any, Any]
 
 
 dask_available = module_available("dask")
 
 
-class DaskManager(ChunkManagerEntrypoint["DaskArray"]):  # type: ignore[type-var]
+class DaskManager(ChunkManagerEntrypoint["DaskArray"]):
     array_cls: type[DaskArray]
     available: bool = dask_available
 
@@ -91,7 +91,7 @@ def array_api(self) -> Any:
 
         return da
 
-    def reduction(  # type: ignore[override]
+    def reduction(
         self,
         arr: T_ChunkedArray,
         func: Callable[..., Any],
@@ -113,7 +113,7 @@ def reduction(  # type: ignore[override]
             keepdims=keepdims,
         )  # type: ignore[no-untyped-call]
 
-    def scan(  # type: ignore[override]
+    def scan(
         self,
         func: Callable[..., Any],
         binop: Callable[..., Any],
diff --git a/xarray/tests/test_backends.py b/xarray/tests/test_backends.py
index 0b90a05262d..152a9ec40e9 100644
--- a/xarray/tests/test_backends.py
+++ b/xarray/tests/test_backends.py
@@ -568,7 +568,7 @@ def test_roundtrip_cftime_datetime_data(self) -> None:
                     assert actual.t.encoding["calendar"] == expected_calendar
 
     def test_roundtrip_timedelta_data(self) -> None:
-        time_deltas = pd.to_timedelta(["1h", "2h", "NaT"])
+        time_deltas = pd.to_timedelta(["1h", "2h", "NaT"])  # type: ignore[arg-type]  #https://github.com/pandas-dev/pandas-stubs/issues/956
         expected = Dataset({"td": ("td", time_deltas), "td0": time_deltas[0]})
         with self.roundtrip(expected) as actual:
             assert_identical(expected, actual)
@@ -5627,7 +5627,9 @@ def test_h5netcdf_entrypoint(tmp_path: Path) -> None:
 
 @requires_netCDF4
 @pytest.mark.parametrize("str_type", (str, np.str_))
-def test_write_file_from_np_str(str_type, tmpdir) -> None:
+def test_write_file_from_np_str(
+    str_type: type[str] | type[np.str_], tmpdir: str
+) -> None:
     # https://github.com/pydata/xarray/pull/5264
     scenarios = [str_type(v) for v in ["scenario_a", "scenario_b", "scenario_c"]]
     years = range(2015, 2100 + 1)
@@ -5638,7 +5640,7 @@ def test_write_file_from_np_str(str_type, tmpdir) -> None:
     )
     tdf.index.name = "scenario"
     tdf.columns.name = "year"
-    tdf = tdf.stack()
+    tdf = cast(pd.DataFrame, tdf.stack())
     tdf.name = "tas"
 
     txr = tdf.to_xarray()
diff --git a/xarray/tests/test_cftime_offsets.py b/xarray/tests/test_cftime_offsets.py
index eabb7d2f4d6..78aa49c7f83 100644
--- a/xarray/tests/test_cftime_offsets.py
+++ b/xarray/tests/test_cftime_offsets.py
@@ -511,7 +511,7 @@ def test_Microsecond_multiplied_float_error():
     ],
     ids=_id_func,
 )
-def test_neg(offset, expected):
+def test_neg(offset: BaseCFTimeOffset, expected: BaseCFTimeOffset) -> None:
     assert -offset == expected
 
 
diff --git a/xarray/tests/test_cftimeindex.py b/xarray/tests/test_cftimeindex.py
index f6eb15fa373..116487e2bcf 100644
--- a/xarray/tests/test_cftimeindex.py
+++ b/xarray/tests/test_cftimeindex.py
@@ -679,11 +679,11 @@ def test_indexing_in_series_loc(series, index, scalar_args, range_args):
 
 @requires_cftime
 def test_indexing_in_series_iloc(series, index):
-    expected = 1
-    assert series.iloc[0] == expected
+    expected1 = 1
+    assert series.iloc[0] == expected1
 
-    expected = pd.Series([1, 2], index=index[:2])
-    assert series.iloc[:2].equals(expected)
+    expected2 = pd.Series([1, 2], index=index[:2])
+    assert series.iloc[:2].equals(expected2)
 
 
 @requires_cftime
@@ -696,27 +696,27 @@ def test_series_dropna(index):
 
 @requires_cftime
 def test_indexing_in_dataframe_loc(df, index, scalar_args, range_args):
-    expected = pd.Series([1], name=index[0])
+    expected_s = pd.Series([1], name=index[0])
     for arg in scalar_args:
-        result = df.loc[arg]
-        assert result.equals(expected)
+        result_s = df.loc[arg]
+        assert result_s.equals(expected_s)
 
-    expected = pd.DataFrame([1, 2], index=index[:2])
+    expected_df = pd.DataFrame([1, 2], index=index[:2])
     for arg in range_args:
-        result = df.loc[arg]
-        assert result.equals(expected)
+        result_df = df.loc[arg]
+        assert result_df.equals(expected_df)
 
 
 @requires_cftime
 def test_indexing_in_dataframe_iloc(df, index):
-    expected = pd.Series([1], name=index[0])
-    result = df.iloc[0]
-    assert result.equals(expected)
-    assert result.equals(expected)
+    expected_s = pd.Series([1], name=index[0])
+    result_s = df.iloc[0]
+    assert result_s.equals(expected_s)
+    assert result_s.equals(expected_s)
 
-    expected = pd.DataFrame([1, 2], index=index[:2])
-    result = df.iloc[:2]
-    assert result.equals(expected)
+    expected_df = pd.DataFrame([1, 2], index=index[:2])
+    result_df = df.iloc[:2]
+    assert result_df.equals(expected_df)
 
 
 @requires_cftime
@@ -957,17 +957,17 @@ def test_cftimeindex_shift(index, freq) -> None:
 
 
 @requires_cftime
-def test_cftimeindex_shift_invalid_n() -> None:
+def test_cftimeindex_shift_invalid_periods() -> None:
     index = xr.cftime_range("2000", periods=3)
     with pytest.raises(TypeError):
-        index.shift("a", "D")
+        index.shift("a", "D")  # type: ignore[arg-type]
 
 
 @requires_cftime
 def test_cftimeindex_shift_invalid_freq() -> None:
     index = xr.cftime_range("2000", periods=3)
     with pytest.raises(TypeError):
-        index.shift(1, 1)
+        index.shift(1, 1)  # type: ignore[arg-type]
 
 
 @requires_cftime
diff --git a/xarray/tests/test_cftimeindex_resample.py b/xarray/tests/test_cftimeindex_resample.py
index 98d4377706c..3dda7a5f1eb 100644
--- a/xarray/tests/test_cftimeindex_resample.py
+++ b/xarray/tests/test_cftimeindex_resample.py
@@ -10,6 +10,7 @@
 
 import xarray as xr
 from xarray.coding.cftime_offsets import _new_to_legacy_freq
+from xarray.coding.cftimeindex import CFTimeIndex
 from xarray.core.pdcompat import _convert_base_to_offset
 from xarray.core.resample_cftime import CFTimeGrouper
 
@@ -204,7 +205,9 @@ def test_calendars(calendar: str) -> None:
         .mean()
     )
     # TODO (benbovy - flexible indexes): update when CFTimeIndex is a xarray Index subclass
-    da_cftime["time"] = da_cftime.xindexes["time"].to_pandas_index().to_datetimeindex()
+    new_pd_index = da_cftime.xindexes["time"].to_pandas_index()
+    assert isinstance(new_pd_index, CFTimeIndex)  # shouldn't that be a pd.Index?
+    da_cftime["time"] = new_pd_index.to_datetimeindex()
     xr.testing.assert_identical(da_cftime, da_datetime)
 
 
@@ -248,11 +251,11 @@ def test_base_and_offset_error():
 
 
 @pytest.mark.parametrize("offset", ["foo", "5MS", 10])
-def test_invalid_offset_error(offset) -> None:
+def test_invalid_offset_error(offset: str | int) -> None:
     cftime_index = xr.cftime_range("2000", periods=5)
     da_cftime = da(cftime_index)
     with pytest.raises(ValueError, match="offset must be"):
-        da_cftime.resample(time="2D", offset=offset)
+        da_cftime.resample(time="2D", offset=offset)  # type: ignore[arg-type]
 
 
 def test_timedelta_offset() -> None:
@@ -279,7 +282,9 @@ def test_resample_loffset_cftimeindex(loffset) -> None:
         result = da_cftimeindex.resample(time="24h", loffset=loffset).mean()
         expected = da_datetimeindex.resample(time="24h", loffset=loffset).mean()
 
-    result["time"] = result.xindexes["time"].to_pandas_index().to_datetimeindex()
+    index = result.xindexes["time"].to_pandas_index()
+    assert isinstance(index, CFTimeIndex)
+    result["time"] = index.to_datetimeindex()
     xr.testing.assert_identical(result, expected)
 
 
diff --git a/xarray/tests/test_coding_times.py b/xarray/tests/test_coding_times.py
index 623e4e9f970..ef478af8786 100644
--- a/xarray/tests/test_coding_times.py
+++ b/xarray/tests/test_coding_times.py
@@ -3,6 +3,7 @@
 import warnings
 from datetime import timedelta
 from itertools import product
+from typing import Literal
 
 import numpy as np
 import pandas as pd
@@ -144,15 +145,15 @@ def test_cf_datetime(num_dates, units, calendar) -> None:
     # we could do this check with near microsecond accuracy:
     # https://github.com/Unidata/netcdf4-python/issues/355
     assert (abs_diff <= np.timedelta64(1, "s")).all()
-    encoded, _, _ = encode_cf_datetime(actual, units, calendar)
+    encoded1, _, _ = encode_cf_datetime(actual, units, calendar)
+    assert_array_equal(num_dates, np.around(encoded1, 1))
 
-    assert_duckarray_allclose(num_dates, encoded)
     if hasattr(num_dates, "ndim") and num_dates.ndim == 1 and "1000" not in units:
         # verify that wrapping with a pandas.Index works
         # note that it *does not* currently work to put
         # non-datetime64 compatible dates into a pandas.Index
-        encoded, _, _ = encode_cf_datetime(pd.Index(actual), units, calendar)
-        assert_duckarray_allclose(num_dates, encoded)
+        encoded2, _, _ = encode_cf_datetime(pd.Index(actual), units, calendar)
+        assert_array_equal(num_dates, np.around(encoded2, 1))
 
 
 @requires_cftime
@@ -627,10 +628,10 @@ def test_cf_timedelta_2d() -> None:
 @pytest.mark.parametrize(
     ["deltas", "expected"],
     [
-        (pd.to_timedelta(["1 day", "2 days"]), "days"),
-        (pd.to_timedelta(["1h", "1 day 1 hour"]), "hours"),
-        (pd.to_timedelta(["1m", "2m", np.nan]), "minutes"),
-        (pd.to_timedelta(["1m3s", "1m4s"]), "seconds"),
+        (pd.to_timedelta(["1 day", "2 days"]), "days"),  # type: ignore[arg-type]  #https://github.com/pandas-dev/pandas-stubs/issues/956
+        (pd.to_timedelta(["1h", "1 day 1 hour"]), "hours"),  # type: ignore[arg-type]  #https://github.com/pandas-dev/pandas-stubs/issues/956
+        (pd.to_timedelta(["1m", "2m", np.nan]), "minutes"),  # type: ignore[arg-type]  #https://github.com/pandas-dev/pandas-stubs/issues/956
+        (pd.to_timedelta(["1m3s", "1m4s"]), "seconds"),  # type: ignore[arg-type]  #https://github.com/pandas-dev/pandas-stubs/issues/956
     ],
 )
 def test_infer_timedelta_units(deltas, expected) -> None:
@@ -1237,7 +1238,7 @@ def test_contains_cftime_lazy() -> None:
 )
 def test_roundtrip_datetime64_nanosecond_precision(
     timestr: str,
-    timeunit: str,
+    timeunit: Literal["ns", "us"],
     dtype: np.typing.DTypeLike,
     fill_value: int | float | None,
     use_encoding: bool,
@@ -1433,8 +1434,8 @@ def test_roundtrip_float_times() -> None:
 def test_encode_cf_datetime_datetime64_via_dask(freq, units, dtype) -> None:
     import dask.array
 
-    times = pd.date_range(start="1700", freq=freq, periods=3)
-    times = dask.array.from_array(times, chunks=1)
+    times_pd = pd.date_range(start="1700", freq=freq, periods=3)
+    times = dask.array.from_array(times_pd, chunks=1)
     encoded_times, encoding_units, encoding_calendar = encode_cf_datetime(
         times, units, None, dtype
     )
@@ -1484,8 +1485,8 @@ def test_encode_cf_datetime_cftime_datetime_via_dask(units, dtype) -> None:
     import dask.array
 
     calendar = "standard"
-    times = cftime_range(start="1700", freq="D", periods=3, calendar=calendar)
-    times = dask.array.from_array(times, chunks=1)
+    times_idx = cftime_range(start="1700", freq="D", periods=3, calendar=calendar)
+    times = dask.array.from_array(times_idx, chunks=1)
     encoded_times, encoding_units, encoding_calendar = encode_cf_datetime(
         times, units, None, dtype
     )
@@ -1557,11 +1558,13 @@ def test_encode_cf_datetime_casting_overflow_error(use_cftime, use_dask, dtype)
 @pytest.mark.parametrize(
     ("units", "dtype"), [("days", np.dtype("int32")), (None, None)]
 )
-def test_encode_cf_timedelta_via_dask(units, dtype) -> None:
+def test_encode_cf_timedelta_via_dask(
+    units: str | None, dtype: np.dtype | None
+) -> None:
     import dask.array
 
-    times = pd.timedelta_range(start="0D", freq="D", periods=3)
-    times = dask.array.from_array(times, chunks=1)
+    times_pd = pd.timedelta_range(start="0D", freq="D", periods=3)
+    times = dask.array.from_array(times_pd, chunks=1)
     encoded_times, encoding_units = encode_cf_timedelta(times, units, dtype)
 
     assert is_duck_dask_array(encoded_times)
diff --git a/xarray/tests/test_concat.py b/xarray/tests/test_concat.py
index 0c570de3b52..8b2a7ec5d28 100644
--- a/xarray/tests/test_concat.py
+++ b/xarray/tests/test_concat.py
@@ -1,7 +1,7 @@
 from __future__ import annotations
 
 from copy import deepcopy
-from typing import TYPE_CHECKING, Any, Callable
+from typing import TYPE_CHECKING, Any, Callable, Literal
 
 import numpy as np
 import pandas as pd
@@ -474,7 +474,7 @@ def data(self, request) -> Dataset:
             "dim3"
         )
 
-    def rectify_dim_order(self, data, dataset) -> Dataset:
+    def rectify_dim_order(self, data: Dataset, dataset) -> Dataset:
         # return a new dataset with all variable dimensions transposed into
         # the order in which they are found in `data`
         return Dataset(
@@ -487,11 +487,13 @@ def rectify_dim_order(self, data, dataset) -> Dataset:
     @pytest.mark.parametrize(
         "dim,data", [["dim1", True], ["dim2", False]], indirect=["data"]
     )
-    def test_concat_simple(self, data, dim, coords) -> None:
+    def test_concat_simple(self, data: Dataset, dim, coords) -> None:
         datasets = [g for _, g in data.groupby(dim, squeeze=False)]
         assert_identical(data, concat(datasets, dim, coords=coords))
 
-    def test_concat_merge_variables_present_in_some_datasets(self, data) -> None:
+    def test_concat_merge_variables_present_in_some_datasets(
+        self, data: Dataset
+    ) -> None:
         # coordinates present in some datasets but not others
         ds1 = Dataset(data_vars={"a": ("y", [0.1])}, coords={"x": 0.1})
         ds2 = Dataset(data_vars={"a": ("y", [0.2])}, coords={"z": 0.2})
@@ -515,7 +517,7 @@ def test_concat_merge_variables_present_in_some_datasets(self, data) -> None:
         assert_identical(expected, actual)
 
     @pytest.mark.parametrize("data", [False], indirect=["data"])
-    def test_concat_2(self, data) -> None:
+    def test_concat_2(self, data: Dataset) -> None:
         dim = "dim2"
         datasets = [g.squeeze(dim) for _, g in data.groupby(dim, squeeze=False)]
         concat_over = [k for k, v in data.coords.items() if dim in v.dims and k != dim]
@@ -524,7 +526,9 @@ def test_concat_2(self, data) -> None:
 
     @pytest.mark.parametrize("coords", ["different", "minimal", "all"])
     @pytest.mark.parametrize("dim", ["dim1", "dim2"])
-    def test_concat_coords_kwarg(self, data, dim, coords) -> None:
+    def test_concat_coords_kwarg(
+        self, data: Dataset, dim: str, coords: Literal["all", "minimal", "different"]
+    ) -> None:
         data = data.copy(deep=True)
         # make sure the coords argument behaves as expected
         data.coords["extra"] = ("dim4", np.arange(3))
@@ -538,7 +542,7 @@ def test_concat_coords_kwarg(self, data, dim, coords) -> None:
         else:
             assert_equal(data["extra"], actual["extra"])
 
-    def test_concat(self, data) -> None:
+    def test_concat(self, data: Dataset) -> None:
         split_data = [
             data.isel(dim1=slice(3)),
             data.isel(dim1=3),
@@ -546,7 +550,7 @@ def test_concat(self, data) -> None:
         ]
         assert_identical(data, concat(split_data, "dim1"))
 
-    def test_concat_dim_precedence(self, data) -> None:
+    def test_concat_dim_precedence(self, data: Dataset) -> None:
         # verify that the dim argument takes precedence over
         # concatenating dataset variables of the same name
         dim = (2 * data["dim1"]).rename("dim1")
diff --git a/xarray/tests/test_conventions.py b/xarray/tests/test_conventions.py
index fdfea3c3fe8..dc0b270dc51 100644
--- a/xarray/tests/test_conventions.py
+++ b/xarray/tests/test_conventions.py
@@ -119,7 +119,7 @@ def test_incompatible_attributes(self) -> None:
             Variable(
                 ["t"], pd.date_range("2000-01-01", periods=3), {"units": "foobar"}
             ),
-            Variable(["t"], pd.to_timedelta(["1 day"]), {"units": "foobar"}),
+            Variable(["t"], pd.to_timedelta(["1 day"]), {"units": "foobar"}),  # type: ignore[arg-type]  #https://github.com/pandas-dev/pandas-stubs/issues/956
             Variable(["t"], [0, 1, 2], {"add_offset": 0}, {"add_offset": 2}),
             Variable(["t"], [0, 1, 2], {"_FillValue": 0}, {"_FillValue": 2}),
         ]
diff --git a/xarray/tests/test_dataarray.py b/xarray/tests/test_dataarray.py
index 44ef486e5d6..b689bb8c02d 100644
--- a/xarray/tests/test_dataarray.py
+++ b/xarray/tests/test_dataarray.py
@@ -341,12 +341,15 @@ def test_constructor(self) -> None:
         assert_identical(expected, actual)
 
         # list coords, w dims
-        coords1 = [["a", "b"], [-1, -2, -3]]
+        coords1: list[Any] = [["a", "b"], [-1, -2, -3]]
         actual = DataArray(data, coords1, ["x", "y"])
         assert_identical(expected, actual)
 
         # pd.Index coords, w dims
-        coords2 = [pd.Index(["a", "b"], name="A"), pd.Index([-1, -2, -3], name="B")]
+        coords2: list[pd.Index] = [
+            pd.Index(["a", "b"], name="A"),
+            pd.Index([-1, -2, -3], name="B"),
+        ]
         actual = DataArray(data, coords2, ["x", "y"])
         assert_identical(expected, actual)
 
@@ -424,7 +427,7 @@ def test_constructor_invalid(self) -> None:
             DataArray(np.random.rand(4, 4), [("x", self.mindex), ("level_1", range(4))])
 
     def test_constructor_from_self_described(self) -> None:
-        data = [[-0.1, 21], [0, 2]]
+        data: list[list[float]] = [[-0.1, 21], [0, 2]]
         expected = DataArray(
             data,
             coords={"x": ["a", "b"], "y": [-1, -2]},
@@ -2488,7 +2491,7 @@ def test_stack_unstack(self) -> None:
         # test GH3000
         a = orig[:0, :1].stack(new_dim=("x", "y")).indexes["new_dim"]
         b = pd.MultiIndex(
-            levels=[pd.Index([], np.int64), pd.Index([0], np.int64)],
+            levels=[pd.Index([], dtype=np.int64), pd.Index([0], dtype=np.int64)],
             codes=[[], []],
             names=["x", "y"],
         )
@@ -3331,28 +3334,28 @@ def test_broadcast_coordinates(self) -> None:
 
     def test_to_pandas(self) -> None:
         # 0d
-        actual = DataArray(42).to_pandas()
+        actual_xr = DataArray(42).to_pandas()
         expected = np.array(42)
-        assert_array_equal(actual, expected)
+        assert_array_equal(actual_xr, expected)
 
         # 1d
         values = np.random.randn(3)
         index = pd.Index(["a", "b", "c"], name="x")
         da = DataArray(values, coords=[index])
-        actual = da.to_pandas()
-        assert_array_equal(actual.values, values)
-        assert_array_equal(actual.index, index)
-        assert_array_equal(actual.index.name, "x")
+        actual_s = da.to_pandas()
+        assert_array_equal(np.asarray(actual_s.values), values)
+        assert_array_equal(actual_s.index, index)
+        assert_array_equal(actual_s.index.name, "x")
 
         # 2d
         values = np.random.randn(3, 2)
         da = DataArray(
             values, coords=[("x", ["a", "b", "c"]), ("y", [0, 1])], name="foo"
         )
-        actual = da.to_pandas()
-        assert_array_equal(actual.values, values)
-        assert_array_equal(actual.index, ["a", "b", "c"])
-        assert_array_equal(actual.columns, [0, 1])
+        actual_df = da.to_pandas()
+        assert_array_equal(np.asarray(actual_df.values), values)
+        assert_array_equal(actual_df.index, ["a", "b", "c"])
+        assert_array_equal(actual_df.columns, [0, 1])
 
         # roundtrips
         for shape in [(3,), (3, 4)]:
@@ -3369,24 +3372,24 @@ def test_to_dataframe(self) -> None:
         arr_np = np.random.randn(3, 4)
 
         arr = DataArray(arr_np, [("B", [1, 2, 3]), ("A", list("cdef"))], name="foo")
-        expected = arr.to_series()
-        actual = arr.to_dataframe()["foo"]
-        assert_array_equal(expected.values, actual.values)
-        assert_array_equal(expected.name, actual.name)
-        assert_array_equal(expected.index.values, actual.index.values)
+        expected_s = arr.to_series()
+        actual_s = arr.to_dataframe()["foo"]
+        assert_array_equal(np.asarray(expected_s.values), np.asarray(actual_s.values))
+        assert_array_equal(np.asarray(expected_s.name), np.asarray(actual_s.name))
+        assert_array_equal(expected_s.index.values, actual_s.index.values)
 
-        actual = arr.to_dataframe(dim_order=["A", "B"])["foo"]
-        assert_array_equal(arr_np.transpose().reshape(-1), actual.values)
+        actual_s = arr.to_dataframe(dim_order=["A", "B"])["foo"]
+        assert_array_equal(arr_np.transpose().reshape(-1), np.asarray(actual_s.values))
 
         # regression test for coords with different dimensions
         arr.coords["C"] = ("B", [-1, -2, -3])
-        expected = arr.to_series().to_frame()
-        expected["C"] = [-1] * 4 + [-2] * 4 + [-3] * 4
-        expected = expected[["C", "foo"]]
-        actual = arr.to_dataframe()
-        assert_array_equal(expected.values, actual.values)
-        assert_array_equal(expected.columns.values, actual.columns.values)
-        assert_array_equal(expected.index.values, actual.index.values)
+        expected_df = arr.to_series().to_frame()
+        expected_df["C"] = [-1] * 4 + [-2] * 4 + [-3] * 4
+        expected_df = expected_df[["C", "foo"]]
+        actual_df = arr.to_dataframe()
+        assert_array_equal(np.asarray(expected_df.values), np.asarray(actual_df.values))
+        assert_array_equal(expected_df.columns.values, actual_df.columns.values)
+        assert_array_equal(expected_df.index.values, actual_df.index.values)
 
         with pytest.raises(ValueError, match="does not match the set of dimensions"):
             arr.to_dataframe(dim_order=["B", "A", "C"])
@@ -3407,11 +3410,13 @@ def test_to_dataframe_multiindex(self) -> None:
         arr = DataArray(arr_np, [("MI", mindex), ("C", [5, 6, 7])], name="foo")
 
         actual = arr.to_dataframe()
-        assert_array_equal(actual["foo"].values, arr_np.flatten())
-        assert_array_equal(actual.index.names, list("ABC"))
-        assert_array_equal(actual.index.levels[0], [1, 2])
-        assert_array_equal(actual.index.levels[1], ["a", "b"])
-        assert_array_equal(actual.index.levels[2], [5, 6, 7])
+        index_pd = actual.index
+        assert isinstance(index_pd, pd.MultiIndex)
+        assert_array_equal(np.asarray(actual["foo"].values), arr_np.flatten())
+        assert_array_equal(index_pd.names, list("ABC"))
+        assert_array_equal(index_pd.levels[0], [1, 2])
+        assert_array_equal(index_pd.levels[1], ["a", "b"])
+        assert_array_equal(index_pd.levels[2], [5, 6, 7])
 
     def test_to_dataframe_0length(self) -> None:
         # regression test for #3008
@@ -3431,10 +3436,10 @@ def test_to_dataframe_0length(self) -> None:
     def test_to_dask_dataframe(self) -> None:
         arr_np = np.arange(3 * 4).reshape(3, 4)
         arr = DataArray(arr_np, [("B", [1, 2, 3]), ("A", list("cdef"))], name="foo")
-        expected = arr.to_series()
+        expected_s = arr.to_series()
         actual = arr.to_dask_dataframe()["foo"]
 
-        assert_array_equal(actual.values, expected.values)
+        assert_array_equal(actual.values, np.asarray(expected_s.values))
 
         actual = arr.to_dask_dataframe(dim_order=["A", "B"])["foo"]
         assert_array_equal(arr_np.transpose().reshape(-1), actual.values)
@@ -3442,13 +3447,15 @@ def test_to_dask_dataframe(self) -> None:
         # regression test for coords with different dimensions
 
         arr.coords["C"] = ("B", [-1, -2, -3])
-        expected = arr.to_series().to_frame()
-        expected["C"] = [-1] * 4 + [-2] * 4 + [-3] * 4
-        expected = expected[["C", "foo"]]
+        expected_df = arr.to_series().to_frame()
+        expected_df["C"] = [-1] * 4 + [-2] * 4 + [-3] * 4
+        expected_df = expected_df[["C", "foo"]]
         actual = arr.to_dask_dataframe()[["C", "foo"]]
 
-        assert_array_equal(expected.values, actual.values)
-        assert_array_equal(expected.columns.values, actual.columns.values)
+        assert_array_equal(expected_df.values, np.asarray(actual.values))
+        assert_array_equal(
+            expected_df.columns.values, np.asarray(actual.columns.values)
+        )
 
         with pytest.raises(ValueError, match="does not match the set of dimensions"):
             arr.to_dask_dataframe(dim_order=["B", "A", "C"])
@@ -3464,8 +3471,8 @@ def test_to_pandas_name_matches_coordinate(self) -> None:
         # coordinate with same name as array
         arr = DataArray([1, 2, 3], dims="x", name="x")
         series = arr.to_series()
-        assert_array_equal([1, 2, 3], series.values)
-        assert_array_equal([0, 1, 2], series.index.values)
+        assert_array_equal([1, 2, 3], list(series.values))
+        assert_array_equal([0, 1, 2], list(series.index.values))
         assert "x" == series.name
         assert "x" == series.index.name
 
@@ -3544,7 +3551,7 @@ def test_nbytes_does_not_load_data(self) -> None:
 
     def test_to_and_from_empty_series(self) -> None:
         # GH697
-        expected = pd.Series([], dtype=np.float64)
+        expected: pd.Series[Any] = pd.Series([], dtype=np.float64)
         da = DataArray.from_series(expected)
         assert len(da) == 0
         actual = da.to_series()
diff --git a/xarray/tests/test_dataset.py b/xarray/tests/test_dataset.py
index fd511af0dfb..4db005ca3fb 100644
--- a/xarray/tests/test_dataset.py
+++ b/xarray/tests/test_dataset.py
@@ -39,6 +39,7 @@
 from xarray.core.common import duck_array_ops, full_like
 from xarray.core.coordinates import Coordinates, DatasetCoordinates
 from xarray.core.indexes import Index, PandasIndex
+from xarray.core.types import ArrayLike
 from xarray.core.utils import is_scalar
 from xarray.namedarray.pycompat import array_type, integer_types
 from xarray.testing import _assert_internal_invariants
@@ -580,6 +581,7 @@ def test_constructor_pandas_single(self) -> None:
             pandas_obj = a.to_pandas()
             ds_based_on_pandas = Dataset(pandas_obj)  # type: ignore  # TODO: improve typing of __init__
             for dim in ds_based_on_pandas.data_vars:
+                assert isinstance(dim, int)
                 assert_array_equal(ds_based_on_pandas[dim], pandas_obj[dim])
 
     def test_constructor_compat(self) -> None:
@@ -1694,7 +1696,7 @@ def test_sel_categorical_error(self) -> None:
         with pytest.raises(ValueError):
             ds.sel(ind="bar", method="nearest")
         with pytest.raises(ValueError):
-            ds.sel(ind="bar", tolerance="nearest")
+            ds.sel(ind="bar", tolerance="nearest")  # type: ignore[arg-type]
 
     def test_categorical_index(self) -> None:
         cat = pd.CategoricalIndex(
@@ -2044,9 +2046,9 @@ def test_to_pandas(self) -> None:
         y = np.random.randn(10)
         t = list("abcdefghij")
         ds = Dataset({"a": ("t", x), "b": ("t", y), "t": ("t", t)})
-        actual = ds.to_pandas()
-        expected = ds.to_dataframe()
-        assert expected.equals(actual), (expected, actual)
+        actual_df = ds.to_pandas()
+        expected_df = ds.to_dataframe()
+        assert expected_df.equals(actual_df), (expected_df, actual_df)
 
         # 2D -> error
         x2d = np.random.randn(10, 10)
@@ -3618,6 +3620,7 @@ def test_reset_index_drop_convert(
     def test_reorder_levels(self) -> None:
         ds = create_test_multiindex()
         mindex = ds["x"].to_index()
+        assert isinstance(mindex, pd.MultiIndex)
         midx = mindex.reorder_levels(["level_2", "level_1"])
         midx_coords = Coordinates.from_pandas_multiindex(midx, "x")
         expected = Dataset({}, coords=midx_coords)
@@ -3943,7 +3946,9 @@ def test_to_stacked_array_dtype_dims(self) -> None:
         D = xr.Dataset({"a": a, "b": b})
         sample_dims = ["x"]
         y = D.to_stacked_array("features", sample_dims)
-        assert y.xindexes["features"].to_pandas_index().levels[1].dtype == D.y.dtype
+        mindex = y.xindexes["features"].to_pandas_index()
+        assert isinstance(mindex, pd.MultiIndex)
+        assert mindex.levels[1].dtype == D.y.dtype
         assert y.dims == ("x", "features")
 
     def test_to_stacked_array_to_unstacked_dataset(self) -> None:
@@ -4114,9 +4119,9 @@ def test_virtual_variables_default_coords(self) -> None:
     def test_virtual_variables_time(self) -> None:
         # access virtual variables
         data = create_test_data()
-        assert_array_equal(
-            data["time.month"].values, data.variables["time"].to_index().month
-        )
+        index = data.variables["time"].to_index()
+        assert isinstance(index, pd.DatetimeIndex)
+        assert_array_equal(data["time.month"].values, index.month)
         assert_array_equal(data["time.season"].values, "DJF")
         # test virtual variable math
         assert_array_equal(data["time.dayofyear"] + 1, 2 + np.arange(20))
@@ -4805,20 +4810,20 @@ def test_to_and_from_dataframe(self) -> None:
 
         # check pathological cases
         df = pd.DataFrame([1])
-        actual = Dataset.from_dataframe(df)
-        expected = Dataset({0: ("index", [1])}, {"index": [0]})
-        assert_identical(expected, actual)
+        actual_ds = Dataset.from_dataframe(df)
+        expected_ds = Dataset({0: ("index", [1])}, {"index": [0]})
+        assert_identical(expected_ds, actual_ds)
 
         df = pd.DataFrame()
-        actual = Dataset.from_dataframe(df)
-        expected = Dataset(coords={"index": []})
-        assert_identical(expected, actual)
+        actual_ds = Dataset.from_dataframe(df)
+        expected_ds = Dataset(coords={"index": []})
+        assert_identical(expected_ds, actual_ds)
 
         # GH697
         df = pd.DataFrame({"A": []})
-        actual = Dataset.from_dataframe(df)
-        expected = Dataset({"A": DataArray([], dims=("index",))}, {"index": []})
-        assert_identical(expected, actual)
+        actual_ds = Dataset.from_dataframe(df)
+        expected_ds = Dataset({"A": DataArray([], dims=("index",))}, {"index": []})
+        assert_identical(expected_ds, actual_ds)
 
         # regression test for GH278
         # use int64 to ensure consistent results for the pandas .equals method
@@ -4857,7 +4862,7 @@ def test_from_dataframe_categorical_index(self) -> None:
     def test_from_dataframe_categorical_index_string_categories(self) -> None:
         cat = pd.CategoricalIndex(
             pd.Categorical.from_codes(
-                np.array([1, 1, 0, 2]),
+                np.array([1, 1, 0, 2], dtype=np.int64),  # type: ignore[arg-type]
                 categories=pd.Index(["foo", "bar", "baz"], dtype="string"),
             )
         )
@@ -4942,7 +4947,7 @@ def test_from_dataframe_unsorted_levels(self) -> None:
     def test_from_dataframe_non_unique_columns(self) -> None:
         # regression test for GH449
         df = pd.DataFrame(np.zeros((2, 2)))
-        df.columns = ["foo", "foo"]
+        df.columns = ["foo", "foo"]  # type: ignore[assignment]
         with pytest.raises(ValueError, match=r"non-unique columns"):
             Dataset.from_dataframe(df)
 
@@ -7231,6 +7236,7 @@ def test_cumulative_integrate(dask) -> None:
 @pytest.mark.parametrize("which_datetime", ["np", "cftime"])
 def test_trapezoid_datetime(dask, which_datetime) -> None:
     rs = np.random.RandomState(42)
+    coord: ArrayLike
     if which_datetime == "np":
         coord = np.array(
             [
diff --git a/xarray/tests/test_formatting.py b/xarray/tests/test_formatting.py
index 9d0eb81bace..0bd8abc3a70 100644
--- a/xarray/tests/test_formatting.py
+++ b/xarray/tests/test_formatting.py
@@ -118,9 +118,9 @@ def test_format_items(self) -> None:
                 np.arange(4) * np.timedelta64(500, "ms"),
                 "00:00:00 00:00:00.500000 00:00:01 00:00:01.500000",
             ),
-            (pd.to_timedelta(["NaT", "0s", "1s", "NaT"]), "NaT 00:00:00 00:00:01 NaT"),
+            (pd.to_timedelta(["NaT", "0s", "1s", "NaT"]), "NaT 00:00:00 00:00:01 NaT"),  # type: ignore[arg-type]  #https://github.com/pandas-dev/pandas-stubs/issues/956
             (
-                pd.to_timedelta(["1 day 1 hour", "1 day", "0 hours"]),
+                pd.to_timedelta(["1 day 1 hour", "1 day", "0 hours"]),  # type: ignore[arg-type]  #https://github.com/pandas-dev/pandas-stubs/issues/956
                 "1 days 01:00:00 1 days 00:00:00 0 days 00:00:00",
             ),
             ([1, 2, 3], "1 2 3"),
diff --git a/xarray/tests/test_groupby.py b/xarray/tests/test_groupby.py
index f0a0fd14d9d..469e5a3b1f2 100644
--- a/xarray/tests/test_groupby.py
+++ b/xarray/tests/test_groupby.py
@@ -734,7 +734,7 @@ def test_groupby_bins_timeseries() -> None:
     expected = xr.DataArray(
         96 * np.ones((14,)),
         dims=["time_bins"],
-        coords={"time_bins": pd.cut(time_bins, time_bins).categories},
+        coords={"time_bins": pd.cut(time_bins, time_bins).categories},  # type: ignore[arg-type]
     ).to_dataset(name="val")
     assert_identical(actual, expected)
 
@@ -868,7 +868,7 @@ def test_groupby_dataset_errors() -> None:
     with pytest.raises(ValueError, match=r"length does not match"):
         data.groupby(data["dim1"][:3])
     with pytest.raises(TypeError, match=r"`group` must be"):
-        data.groupby(data.coords["dim1"].to_index())
+        data.groupby(data.coords["dim1"].to_index())  # type: ignore[arg-type]
 
 
 def test_groupby_dataset_reduce() -> None:
@@ -1624,7 +1624,7 @@ def test_groupby_bins(
         bins = [0, 1.5, 5]
 
         df = array.to_dataframe()
-        df["dim_0_bins"] = pd.cut(array["dim_0"], bins, **cut_kwargs)
+        df["dim_0_bins"] = pd.cut(array["dim_0"], bins, **cut_kwargs)  # type: ignore[call-overload]
 
         expected_df = df.groupby("dim_0_bins", observed=True).sum()
         # TODO: can't convert df with IntervalIndex to Xarray
@@ -1690,7 +1690,7 @@ def test_groupby_bins_empty(self) -> None:
         array = DataArray(np.arange(4), [("x", range(4))])
         # one of these bins will be empty
         bins = [0, 4, 5]
-        bin_coords = pd.cut(array["x"], bins).categories
+        bin_coords = pd.cut(array["x"], bins).categories  # type: ignore[call-overload]
         actual = array.groupby_bins("x", bins).sum()
         expected = DataArray([6, np.nan], dims="x_bins", coords={"x_bins": bin_coords})
         assert_identical(expected, actual)
@@ -1701,7 +1701,7 @@ def test_groupby_bins_empty(self) -> None:
     def test_groupby_bins_multidim(self) -> None:
         array = self.make_groupby_multidim_example_array()
         bins = [0, 15, 20]
-        bin_coords = pd.cut(array["lat"].values.flat, bins).categories
+        bin_coords = pd.cut(array["lat"].values.flat, bins).categories  # type: ignore[call-overload]
         expected = DataArray([16, 40], dims="lat_bins", coords={"lat_bins": bin_coords})
         actual = array.groupby_bins("lat", bins).map(lambda x: x.sum())
         assert_identical(expected, actual)
diff --git a/xarray/tests/test_indexes.py b/xarray/tests/test_indexes.py
index 5ebdfd5da6e..48e254b037b 100644
--- a/xarray/tests/test_indexes.py
+++ b/xarray/tests/test_indexes.py
@@ -410,13 +410,15 @@ def test_stack(self) -> None:
             "y": xr.Variable("y", pd.Index([1, 3, 2])),
         }
 
-        index = PandasMultiIndex.stack(prod_vars, "z")
+        index_xr = PandasMultiIndex.stack(prod_vars, "z")
 
-        assert index.dim == "z"
+        assert index_xr.dim == "z"
+        index_pd = index_xr.index
+        assert isinstance(index_pd, pd.MultiIndex)
         # TODO: change to tuple when pandas 3 is minimum
-        assert list(index.index.names) == ["x", "y"]
+        assert list(index_pd.names) == ["x", "y"]
         np.testing.assert_array_equal(
-            index.index.codes, [[0, 0, 0, 1, 1, 1], [0, 1, 2, 0, 1, 2]]
+            index_pd.codes, [[0, 0, 0, 1, 1, 1], [0, 1, 2, 0, 1, 2]]
         )
 
         with pytest.raises(
@@ -433,13 +435,15 @@ def test_stack_non_unique(self) -> None:
             "y": xr.Variable("y", pd.Index([1, 1, 2])),
         }
 
-        index = PandasMultiIndex.stack(prod_vars, "z")
+        index_xr = PandasMultiIndex.stack(prod_vars, "z")
+        index_pd = index_xr.index
+        assert isinstance(index_pd, pd.MultiIndex)
 
         np.testing.assert_array_equal(
-            index.index.codes, [[0, 0, 0, 1, 1, 1], [0, 0, 1, 0, 0, 1]]
+            index_pd.codes, [[0, 0, 0, 1, 1, 1], [0, 0, 1, 0, 0, 1]]
         )
-        np.testing.assert_array_equal(index.index.levels[0], ["b", "a"])
-        np.testing.assert_array_equal(index.index.levels[1], [1, 2])
+        np.testing.assert_array_equal(index_pd.levels[0], ["b", "a"])
+        np.testing.assert_array_equal(index_pd.levels[1], [1, 2])
 
     def test_unstack(self) -> None:
         pd_midx = pd.MultiIndex.from_product(
@@ -600,10 +604,7 @@ def indexes(
 
         _, variables = indexes_and_vars
 
-        if isinstance(x_idx, Index):
-            index_type = Index
-        else:
-            index_type = pd.Index
+        index_type = Index if isinstance(x_idx, Index) else pd.Index
 
         return Indexes(indexes, variables, index_type=index_type)
 
diff --git a/xarray/tests/test_plot.py b/xarray/tests/test_plot.py
index 578e6bcc18e..a973f6b11f7 100644
--- a/xarray/tests/test_plot.py
+++ b/xarray/tests/test_plot.py
@@ -6,7 +6,7 @@
 from collections.abc import Generator, Hashable
 from copy import copy
 from datetime import date, timedelta
-from typing import Any, Callable, Literal
+from typing import Any, Callable, Literal, cast
 
 import numpy as np
 import pandas as pd
@@ -528,7 +528,7 @@ def test__infer_interval_breaks(self) -> None:
             [-0.5, 0.5, 5.0, 9.5, 10.5], _infer_interval_breaks([0, 1, 9, 10])
         )
         assert_array_equal(
-            pd.date_range("20000101", periods=4) - np.timedelta64(12, "h"),
+            pd.date_range("20000101", periods=4) - np.timedelta64(12, "h"),  # type: ignore[operator]
             _infer_interval_breaks(pd.date_range("20000101", periods=3)),
         )
 
@@ -1048,7 +1048,9 @@ def test_list_levels(self) -> None:
         assert cmap_params["cmap"].N == 5
         assert cmap_params["norm"].N == 6
 
-        for wrap_levels in [list, np.array, pd.Index, DataArray]:
+        for wrap_levels in cast(
+            list[Callable[[Any], dict[Any, Any]]], [list, np.array, pd.Index, DataArray]
+        ):
             cmap_params = _determine_cmap_params(data, levels=wrap_levels(orig_levels))
             assert_array_equal(cmap_params["levels"], orig_levels)
 
diff --git a/xarray/tests/test_rolling.py b/xarray/tests/test_rolling.py
index 89f6ebba2c3..79869e63ae7 100644
--- a/xarray/tests/test_rolling.py
+++ b/xarray/tests/test_rolling.py
@@ -206,9 +206,9 @@ def test_rolling_pandas_compat(
             index=window, center=center, min_periods=min_periods
         ).reduce(np.nanmean)
 
-        np.testing.assert_allclose(s_rolling.values, da_rolling.values)
+        np.testing.assert_allclose(np.asarray(s_rolling.values), da_rolling.values)
         np.testing.assert_allclose(s_rolling.index, da_rolling["index"])
-        np.testing.assert_allclose(s_rolling.values, da_rolling_np.values)
+        np.testing.assert_allclose(np.asarray(s_rolling.values), da_rolling_np.values)
         np.testing.assert_allclose(s_rolling.index, da_rolling_np["index"])
 
     @pytest.mark.parametrize("center", (True, False))
@@ -221,12 +221,14 @@ def test_rolling_construct(self, center: bool, window: int) -> None:
         da_rolling = da.rolling(index=window, center=center, min_periods=1)
 
         da_rolling_mean = da_rolling.construct("window").mean("window")
-        np.testing.assert_allclose(s_rolling.values, da_rolling_mean.values)
+        np.testing.assert_allclose(np.asarray(s_rolling.values), da_rolling_mean.values)
         np.testing.assert_allclose(s_rolling.index, da_rolling_mean["index"])
 
         # with stride
         da_rolling_mean = da_rolling.construct("window", stride=2).mean("window")
-        np.testing.assert_allclose(s_rolling.values[::2], da_rolling_mean.values)
+        np.testing.assert_allclose(
+            np.asarray(s_rolling.values[::2]), da_rolling_mean.values
+        )
         np.testing.assert_allclose(s_rolling.index[::2], da_rolling_mean["index"])
 
         # with fill_value
@@ -649,7 +651,9 @@ def test_rolling_pandas_compat(self, center, window, min_periods) -> None:
             index=window, center=center, min_periods=min_periods
         ).mean()
 
-        np.testing.assert_allclose(df_rolling["x"].values, ds_rolling["x"].values)
+        np.testing.assert_allclose(
+            np.asarray(df_rolling["x"].values), ds_rolling["x"].values
+        )
         np.testing.assert_allclose(df_rolling.index, ds_rolling["index"])
 
     @pytest.mark.parametrize("center", (True, False))
@@ -668,7 +672,9 @@ def test_rolling_construct(self, center: bool, window: int) -> None:
         ds_rolling = ds.rolling(index=window, center=center)
 
         ds_rolling_mean = ds_rolling.construct("window").mean("window")
-        np.testing.assert_allclose(df_rolling["x"].values, ds_rolling_mean["x"].values)
+        np.testing.assert_allclose(
+            np.asarray(df_rolling["x"].values), ds_rolling_mean["x"].values
+        )
         np.testing.assert_allclose(df_rolling.index, ds_rolling_mean["index"])
 
         # with fill_value
@@ -695,7 +701,7 @@ def test_rolling_construct_stride(self, center: bool, window: int) -> None:
         ds_rolling = ds.rolling(index=window, center=center)
         ds_rolling_mean = ds_rolling.construct("w", stride=2).mean("w")
         np.testing.assert_allclose(
-            df_rolling_mean["x"][::2].values, ds_rolling_mean["x"].values
+            np.asarray(df_rolling_mean["x"][::2].values), ds_rolling_mean["x"].values
         )
         np.testing.assert_allclose(df_rolling_mean.index[::2], ds_rolling_mean["index"])
 
@@ -704,7 +710,7 @@ def test_rolling_construct_stride(self, center: bool, window: int) -> None:
         ds2_rolling = ds2.rolling(index=window, center=center)
         ds2_rolling_mean = ds2_rolling.construct("w", stride=2).mean("w")
         np.testing.assert_allclose(
-            df_rolling_mean["x"][::2].values, ds2_rolling_mean["x"].values
+            np.asarray(df_rolling_mean["x"][::2].values), ds2_rolling_mean["x"].values
         )
 
         # Mixed coordinates, indexes and 2D coordinates
diff --git a/xarray/tests/test_variable.py b/xarray/tests/test_variable.py
index 081bf09484a..60c173a9e52 100644
--- a/xarray/tests/test_variable.py
+++ b/xarray/tests/test_variable.py
@@ -2649,7 +2649,7 @@ def test_tz_datetime(self) -> None:
         tz = pytz.timezone("America/New_York")
         times_ns = pd.date_range("2000", periods=1, tz=tz)
 
-        times_s = times_ns.astype(pd.DatetimeTZDtype("s", tz))
+        times_s = times_ns.astype(pd.DatetimeTZDtype("s", tz))  # type: ignore[arg-type]
         with warnings.catch_warnings():
             warnings.simplefilter("ignore")
             actual: T_DuckArray = as_compatible_data(times_s)
@@ -2661,7 +2661,7 @@ def test_tz_datetime(self) -> None:
             warnings.simplefilter("ignore")
             actual2: T_DuckArray = as_compatible_data(series)
 
-        np.testing.assert_array_equal(actual2, series.values)
+        np.testing.assert_array_equal(actual2, np.asarray(series.values))
         assert actual2.dtype == np.dtype("datetime64[ns]")
 
     def test_full_like(self) -> None:
@@ -2978,26 +2978,35 @@ def test_datetime_conversion_warning(values, warns) -> None:
         )
 
 
-def test_pandas_two_only_datetime_conversion_warnings() -> None:
-    # Note these tests rely on pandas features that are only present in pandas
-    # 2.0.0 and above, and so for now cannot be parametrized.
-    cases = [
-        (pd.date_range("2000", periods=1), "datetime64[s]"),
-        (pd.Series(pd.date_range("2000", periods=1)), "datetime64[s]"),
-        (
-            pd.date_range("2000", periods=1, tz=pytz.timezone("America/New_York")),
-            pd.DatetimeTZDtype("s", pytz.timezone("America/New_York")),
+tz_ny = pytz.timezone("America/New_York")
+
+
+@pytest.mark.parametrize(
+    ["data", "dtype"],
+    [
+        pytest.param(pd.date_range("2000", periods=1), "datetime64[s]", id="index-sec"),
+        pytest.param(
+            pd.Series(pd.date_range("2000", periods=1)),
+            "datetime64[s]",
+            id="series-sec",
         ),
-        (
-            pd.Series(
-                pd.date_range("2000", periods=1, tz=pytz.timezone("America/New_York"))
-            ),
-            pd.DatetimeTZDtype("s", pytz.timezone("America/New_York")),
+        pytest.param(
+            pd.date_range("2000", periods=1, tz=tz_ny),
+            pd.DatetimeTZDtype("s", tz_ny),  # type: ignore[arg-type]
+            id="index-timezone",
         ),
-    ]
-    for data, dtype in cases:
-        with pytest.warns(UserWarning, match="non-nanosecond precision datetime"):
-            var = Variable(["time"], data.astype(dtype))
+        pytest.param(
+            pd.Series(pd.date_range("2000", periods=1, tz=tz_ny)),
+            pd.DatetimeTZDtype("s", tz_ny),  # type: ignore[arg-type]
+            id="series-timezone",
+        ),
+    ],
+)
+def test_pandas_two_only_datetime_conversion_warnings(
+    data: pd.DatetimeIndex | pd.Series, dtype: str | pd.DatetimeTZDtype
+) -> None:
+    with pytest.warns(UserWarning, match="non-nanosecond precision datetime"):
+        var = Variable(["time"], data.astype(dtype))  # type: ignore[arg-type]
 
     if var.dtype.kind == "M":
         assert var.dtype == np.dtype("datetime64[ns]")
@@ -3006,9 +3015,7 @@ def test_pandas_two_only_datetime_conversion_warnings() -> None:
         # the case that the variable is backed by a timezone-aware
         # DatetimeIndex, and thus is hidden within the PandasIndexingAdapter class.
         assert isinstance(var._data, PandasIndexingAdapter)
-        assert var._data.array.dtype == pd.DatetimeTZDtype(
-            "ns", pytz.timezone("America/New_York")
-        )
+        assert var._data.array.dtype == pd.DatetimeTZDtype("ns", tz_ny)
 
 
 @pytest.mark.parametrize(
diff --git a/xarray/util/generate_ops.py b/xarray/util/generate_ops.py
index ee4dd68b3ba..a9f66cdc614 100644
--- a/xarray/util/generate_ops.py
+++ b/xarray/util/generate_ops.py
@@ -88,12 +88,10 @@ def {method}(self, other: {other_type}) -> {return_type}:{type_ignore}
         return self._binary_op(other, {func})"""
 template_binop_overload = """
     @overload{overload_type_ignore}
-    def {method}(self, other: {overload_type}) -> {overload_type}:
-        ...
+    def {method}(self, other: {overload_type}) -> {overload_type}: ...
 
     @overload
-    def {method}(self, other: {other_type}) -> {return_type}:
-        ...
+    def {method}(self, other: {other_type}) -> {return_type}: ...
 
     def {method}(self, other: {other_type}) -> {return_type} | {overload_type}:{type_ignore}
         return self._binary_op(other, {func})"""
@@ -129,7 +127,7 @@ def {method}(self, *args: Any, **kwargs: Any) -> Self:
 # The type ignores might not be necessary anymore at some point.
 #
 # We require a "hack" to tell type checkers that e.g. Variable + DataArray = DataArray
-# In reality this returns NotImplementes, but this is not a valid type in python 3.9.
+# In reality this returns NotImplemented, but this is not a valid type in python 3.9.
 # Therefore, we return DataArray. In reality this would call DataArray.__add__(Variable)
 # TODO: change once python 3.10 is the minimum.
 #
@@ -216,6 +214,10 @@ def unops() -> list[OpsType]:
     ]
 
 
+# We use short names T_DA and T_DS to keep below 88 lines so
+# ruff does not reformat everything. When reformatting, the
+# type-ignores end up in the wrong line :/
+
 ops_info = {}
 ops_info["DatasetOpsMixin"] = (
     binops(other_type="DsCompatible") + inplace(other_type="DsCompatible") + unops()
@@ -224,12 +226,12 @@ def unops() -> list[OpsType]:
     binops(other_type="DaCompatible") + inplace(other_type="DaCompatible") + unops()
 )
 ops_info["VariableOpsMixin"] = (
-    binops_overload(other_type="VarCompatible", overload_type="T_DataArray")
+    binops_overload(other_type="VarCompatible", overload_type="T_DA")
     + inplace(other_type="VarCompatible", type_ignore="misc")
     + unops()
 )
 ops_info["DatasetGroupByOpsMixin"] = binops(
-    other_type="GroupByCompatible", return_type="Dataset"
+    other_type="Dataset | DataArray", return_type="Dataset"
 )
 ops_info["DataArrayGroupByOpsMixin"] = binops(
     other_type="T_Xarray", return_type="T_Xarray"
@@ -237,6 +239,7 @@ def unops() -> list[OpsType]:
 
 MODULE_PREAMBLE = '''\
 """Mixin classes with arithmetic operators."""
+
 # This file was generated using xarray.util.generate_ops. Do not edit manually.
 
 from __future__ import annotations
@@ -248,15 +251,15 @@ def unops() -> list[OpsType]:
 from xarray.core.types import (
     DaCompatible,
     DsCompatible,
-    GroupByCompatible,
     Self,
-    T_DataArray,
     T_Xarray,
     VarCompatible,
 )
 
 if TYPE_CHECKING:
-    from xarray.core.dataset import Dataset'''
+    from xarray.core.dataarray import DataArray
+    from xarray.core.dataset import Dataset
+    from xarray.core.types import T_DataArray as T_DA'''
 
 
 CLASS_PREAMBLE = """{newline}