diff --git a/.github/workflows/ci.yaml b/.github/workflows/ci.yaml
index f23b25b8..a4ed450f 100644
--- a/.github/workflows/ci.yaml
+++ b/.github/workflows/ci.yaml
@@ -15,7 +15,7 @@ jobs:
         uses: actions/checkout@v3
       - uses: ./.github/actions/setup
         with:
-          python-version: "3.9"
+          python-version: "3.10"
           venv-id: "docs"
           poetry-dependency-install-flags: "--all-extras --only 'main,dev'"
       # There are still a lot of mypy errors to resolve
@@ -31,7 +31,7 @@ jobs:
         uses: actions/checkout@v3
       - uses: ./.github/actions/setup
         with:
-          python-version: "3.9"
+          python-version: "3.10"
           venv-id: "docs"
           poetry-dependency-install-flags: "--all-extras --only 'main,docs,notebooks'"
       - name: docs
@@ -43,7 +43,7 @@ jobs:
       fail-fast: false
       matrix:
         os: [ "ubuntu-latest" ]
-        python-version: [ "3.9", "3.10", "3.11" ]
+        python-version: [ "3.10", "3.11" ]
     runs-on: "${{ matrix.os }}"
     steps:
       - name: Check out repository
@@ -88,7 +88,7 @@ jobs:
     runs-on: ubuntu-latest
     strategy:
       matrix:
-        python-version: ["3.9"]
+        python-version: ["3.10"]
 
     steps:
       - name: Checkout repository
@@ -107,7 +107,7 @@ jobs:
       fail-fast: false
       matrix:
         os: [ "ubuntu-latest" ]
-        python-version: [ "3.9", "3.10", "3.11" ]
+        python-version: [ "3.10", "3.11" ]
     runs-on: "${{ matrix.os }}"
     steps:
       - name: Check out repository
@@ -127,7 +127,7 @@ jobs:
         uses: actions/checkout@v3
       - uses: ./.github/actions/setup
         with:
-          python-version: "3.9"
+          python-version: "3.10"
           venv-id: "check-build-${{ runner.os }}"
           run-poetry-install: false
           poetry-dependency-install-flags: "not used"
@@ -145,7 +145,7 @@ jobs:
         uses: actions/checkout@v3
       - uses: ./.github/actions/setup
         with:
-          python-version: "3.9"
+          python-version: "3.10"
           venv-id: "licence-check"
           poetry-dependency-install-flags: "--all-extras"
       - name: Check licences of dependencies
diff --git a/.github/workflows/deploy.yaml b/.github/workflows/deploy.yaml
index 2b8e1aae..fd8b56cc 100644
--- a/.github/workflows/deploy.yaml
+++ b/.github/workflows/deploy.yaml
@@ -19,7 +19,7 @@ jobs:
           fetch-depth: 0
       - uses: ./.github/actions/setup
         with:
-          python-version: "3.9"
+          python-version: "3.10"
           venv-id: "deploy"
           poetry-dependency-install-flags: "--all-extras"
       - name: Run tests
diff --git a/.github/workflows/install-conda.yml b/.github/workflows/install-conda.yml
index 4baa0dad..25050dd2 100644
--- a/.github/workflows/install-conda.yml
+++ b/.github/workflows/install-conda.yml
@@ -12,7 +12,7 @@ jobs:
       fail-fast: false
       matrix:
         os: ["ubuntu-latest", "macos-latest", "windows-latest"]
-        python-version: ['3.8', '3.9', '3.10', '3.11']
+        python-version: ['3.10', '3.11']
 
     steps:
     - name: Setup conda
diff --git a/.github/workflows/install.yaml b/.github/workflows/install.yaml
index 278586ca..b51444c4 100644
--- a/.github/workflows/install.yaml
+++ b/.github/workflows/install.yaml
@@ -12,7 +12,7 @@ jobs:
       fail-fast: false
       matrix:
         os: ["ubuntu-latest", "macos-latest", "windows-latest"]
-        python-version: [ "3.9", "3.10", "3.11" ]
+        python-version: [ "3.10", "3.11" ]
     steps:
     - name: Set up Python "${{ matrix.python-version }}"
       id: setup-python
diff --git a/.github/workflows/release.yaml b/.github/workflows/release.yaml
index b483deac..bec1c2f7 100644
--- a/.github/workflows/release.yaml
+++ b/.github/workflows/release.yaml
@@ -19,7 +19,7 @@ jobs:
           fetch-depth: 0
       - uses: ./.github/actions/setup
         with:
-          python-version: "3.9"
+          python-version: "3.10"
           venv-id: "release"
           poetry-dependency-install-flags: "--all-extras"
       - name: Add version to environment
diff --git a/.readthedocs.yaml b/.readthedocs.yaml
index 9543d49f..2ae6ed65 100644
--- a/.readthedocs.yaml
+++ b/.readthedocs.yaml
@@ -11,7 +11,7 @@ version: 2
 build:
   os: ubuntu-22.04
   tools:
-    python: "3.9"
+    python: "3.10"
   jobs:
     post_create_environment:
       - pip install poetry
diff --git a/changelog/321.fix.md b/changelog/321.fix.md
new file mode 100644
index 00000000..04b6afb7
--- /dev/null
+++ b/changelog/321.fix.md
@@ -0,0 +1,8 @@
+Restored compatibility with pandas 3.0 and xarray 2025+ by patching four places where the older APIs are no longer accepted:
+
+- `RunGroupBy.__init__` previously called `numpy.issubdtype(col.dtype, numpy.number)` to detect numeric meta columns, which raises `TypeError` on `pandas.StringDtype` (the new default for inferred string columns). Routed through `pandas.api.types.is_numeric_dtype`.
+- `_xarray._many_to_one` ended with `Series[0]` positional indexing, which pandas 3 has removed. Replaced with `.iloc[0]`.
+- `ScmRun.convert_unit`, `_binary_op` and `_unary_op` wrote results via `self._df.values[:] = ...`. pandas 3 makes `DataFrame.values` return a read-only array, so the in-place write raises `ValueError`. Switched to `self._df.iloc[:, :] = ...`; the binary/unary op sites additionally cast their right-hand side to `float` so that comparison ops (`lt`, `eq`, `ne`, ...) which return `bool` arrays continue to land as `float64` in the underlying numeric block, preserving the prior silent-cast behaviour.
+- `_read_nc` passed `use_cftime=True` to `xarray.load_dataset`, which xarray 2025+ deprecates in favour of `decode_times=xr.coders.CFDatetimeCoder(use_cftime=True)`. The deprecation otherwise fires a `FutureWarning` on every `ScmRun.from_nc()` call. Routes through the new API where available and falls back to the bare kwarg on xarray older than 2024.09.
+
+The previously-failing `ScmRun.groupby`, `ScmRun.to_xarray`, `ScmRun.convert_unit`, `ScmRun.to_nc` / `ScmRun.from_nc`, and the arithmetic and comparison operators on `ScmRun` now all run on both pandas 2 and pandas 3.
diff --git a/pyproject.toml b/pyproject.toml
index 55ac095a..af9bf99b 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -20,15 +20,13 @@ classifiers = [
     "License :: OSI Approved :: BSD License",
     "Intended Audience :: Developers",
     "Operating System :: OS Independent",
-    "Programming Language :: Python :: 3.8",
-    "Programming Language :: Python :: 3.9",
     "Programming Language :: Python :: 3.10",
     "Programming Language :: Python :: 3.11",
 ]
 
 [tool.poetry.dependencies]
 # TODO: get rid of this stupid upper level bound
-python = ">=3.9,<4"
+python = ">=3.10,<4"
 cftime = ">=1.5"
 numpy = "*"
 openscm-units = "*"
@@ -39,10 +37,7 @@ pint-pandas = "*"
 python-dateutil = "*"
 tqdm = "*"
 six = "*"
-xarray = [
-    { version = "*", python = ">=3.10" },
-    { version = "<=2025.03", python = ">=3.9,<3.10" },
-]
+xarray = "*"
 nc-time-axis = { version = ">=1.2.0", optional = true }
 typing-extensions = "*"
 matplotlib = { version = ">=3.7.1", optional = true }
@@ -83,6 +78,7 @@ pre-commit = "^3.3.1"
 towncrier = "^23.6.0"
 liccheck = "^0.9.1"
 pandas-stubs = "<3"
+setuptools = "*"
 
 [tool.poetry.group.notebooks.dependencies]
 myst-nb = "^0.17.0"
diff --git a/src/scmdata/_xarray.py b/src/scmdata/_xarray.py
index c38e4830..a2510a37 100644
--- a/src/scmdata/_xarray.py
+++ b/src/scmdata/_xarray.py
@@ -198,7 +198,10 @@ def _many_to_one(df, col1, col2):
     # thanks https://stackoverflow.com/a/59091549
     checker = df[[col1, col2]].drop_duplicates()
 
-    max_count = checker.groupby(col2).count().max()[0]
+    # ``.iloc[0]`` rather than ``[0]``: pandas 3.0 removed positional
+    # integer indexing on label-indexed Series, so ``[0]`` would raise
+    # ``KeyError: 0`` on the Series returned by the chained ``.max()``.
+    max_count = checker.groupby(col2).count().max().iloc[0]
     if max_count < 1:  # pragma: no cover # emergency valve
         raise AssertionError
 
diff --git a/src/scmdata/groupby.py b/src/scmdata/groupby.py
index b261c5b4..83358205 100644
--- a/src/scmdata/groupby.py
+++ b/src/scmdata/groupby.py
@@ -57,8 +57,12 @@ def __init__(
         m = run.meta.reset_index(drop=True)
         self.na_fill_value = float(na_fill_value)
 
-        # Work around the bad handling of NaN values in groupbys
-        if any([np.issubdtype(m[c].dtype, np.number) for c in m]):
+        # Work around the bad handling of NaN values in groupbys.
+        # pd.api.types.is_numeric_dtype accepts every dtype scmdata
+        # ever emits; np.issubdtype(..., np.number) raises on
+        # pandas 3.0's default StringDtype with
+        # ``TypeError: Cannot interpret '<StringDtype(...)>'``.
+        if any([pd.api.types.is_numeric_dtype(m[c]) for c in m]):
             if (m == na_fill_value).any(axis=None):
                 raise ValueError(
                     "na_fill_value conflicts with data value. Choose a na_fill_value "
diff --git a/src/scmdata/netcdf.py b/src/scmdata/netcdf.py
index 5a7bd8a1..68682df2 100644
--- a/src/scmdata/netcdf.py
+++ b/src/scmdata/netcdf.py
@@ -75,7 +75,13 @@ def _write_nc(
 
 
 def _read_nc(cls: BaseScmRun, fname: FilePath) -> BaseScmRun:
-    loaded = xr.load_dataset(fname, use_cftime=True)
+    try:
+        time_coder = xr.coders.CFDatetimeCoder(use_cftime=True)
+        loaded = xr.load_dataset(fname, decode_times=time_coder)
+    except AttributeError:
+        # xarray older than 2024.09 has no ``xr.coders.CFDatetimeCoder``;
+        # fall back to the deprecated bare ``use_cftime`` kwarg.
+        loaded = xr.load_dataset(fname, use_cftime=True)
     dataframe = loaded.to_dataframe()
 
     dataframe = _reshape_to_scmrun_dataframe(dataframe, loaded)
diff --git a/src/scmdata/run.py b/src/scmdata/run.py
index ef6affce..62be9471 100644
--- a/src/scmdata/run.py
+++ b/src/scmdata/run.py
@@ -745,10 +745,12 @@ def _perform_op(run: Self) -> Self:
             res_stacked = np.vstack(res)
 
             if use_pint:
-                run._df.values[:] = res_stacked.magnitude.T
+                run._df.iloc[:, :] = np.asarray(
+                    res_stacked.magnitude.T, dtype=float
+                )
                 run["unit"] = str(res_stacked.units)
             else:
-                run._df.values[:] = res_stacked.T
+                run._df.iloc[:, :] = np.asarray(res_stacked.T, dtype=float)
             return run
 
         return self.copy().groupby("unit").apply(_perform_op)
@@ -758,7 +760,7 @@ def _unary_op(self, f: Any, *args: Any, **kwargs: Any) -> Self:
 
         res = [f(v) for v in run.values]
 
-        run._df.values[:] = np.vstack(res).T
+        run._df.iloc[:, :] = np.asarray(np.vstack(res).T, dtype=float)
         return run
 
     def drop_meta(self, columns: Iterable[str] | str, inplace: bool = False) -> Self:
@@ -2177,7 +2179,7 @@ def apply_units(group):
             orig_unit = group.get_unique_meta("unit", no_duplicates=True)
             uc = UnitConverter(orig_unit, unit, context=context)
 
-            group._df.values[:] = uc.convert_from(group._df.values)
+            group._df.iloc[:, :] = uc.convert_from(group._df.values)
             group["unit"] = unit
 
             return group
diff --git a/tests/unit/test_netcdf.py b/tests/unit/test_netcdf.py
index b6f087c9..69c7fa9e 100644
--- a/tests/unit/test_netcdf.py
+++ b/tests/unit/test_netcdf.py
@@ -747,3 +747,31 @@ def test_run_to_nc_different_eras(scm_run, shift_times):
 
         res = nc_to_run(scm_run.__class__, out_fname)
     assert_scmdf_almost_equal(scm_run, res)
+
+
+def test_nc_to_run_does_not_emit_use_cftime_futurewarning(scm_run):
+    # Regression test: xarray 2025+ deprecates the bare ``use_cftime``
+    # kwarg on ``xr.load_dataset`` in favour of passing a
+    # ``CFDatetimeCoder`` via ``decode_times``. The deprecation
+    # previously fired a FutureWarning on every ``ScmRun.from_nc()`` /
+    # ``nc_to_run`` call. The fix routes through the new API when
+    # available.
+    import warnings
+
+    if not hasattr(xr, "coders") or not hasattr(xr.coders, "CFDatetimeCoder"):
+        pytest.skip("xarray too old for CFDatetimeCoder; legacy path is fine")
+
+    with tempfile.TemporaryDirectory() as tempdir:
+        out_fname = join(tempdir, "out.nc")
+        run_to_nc(scm_run, out_fname, dimensions=("scenario",))
+
+        with warnings.catch_warnings(record=True) as caught:
+            warnings.simplefilter("always")
+            nc_to_run(scm_run.__class__, out_fname)
+
+        use_cftime_warnings = [
+            w for w in caught
+            if issubclass(w.category, FutureWarning)
+            and "use_cftime" in str(w.message)
+        ]
+    assert not use_cftime_warnings, [str(w.message) for w in use_cftime_warnings]