diff --git a/.github/workflows/ci.yaml b/.github/workflows/ci.yaml
index 5a5ddb0a..e7c52838 100644
--- a/.github/workflows/ci.yaml
+++ b/.github/workflows/ci.yaml
@@ -27,7 +27,7 @@ jobs:
     steps:
       - uses: actions/checkout@v4
       - name: set up conda environment
-        uses: mamba-org/setup-micromamba@v1
+        uses: mamba-org/setup-micromamba@v2
         with:
           environment-file: ci/environment.yml
           init-shell: >-
diff --git a/.github/workflows/upstream-dev-ci.yaml b/.github/workflows/upstream-dev-ci.yaml
index fcfcc470..6d3893ea 100644
--- a/.github/workflows/upstream-dev-ci.yaml
+++ b/.github/workflows/upstream-dev-ci.yaml
@@ -27,7 +27,7 @@ jobs:
       - uses: actions/checkout@v4
       - name: set up conda environment
         id: conda
-        uses: mamba-org/setup-micromamba@v1
+        uses: mamba-org/setup-micromamba@v2
         with:
           environment-file: ci/environment-upstream-dev.yml
           init-shell: >-
diff --git a/xwrf/grid.py b/xwrf/grid.py
index 40e9c34c..1be8151d 100644
--- a/xwrf/grid.py
+++ b/xwrf/grid.py
@@ -72,8 +72,8 @@ def _wrf_grid_from_dataset(ds: xr.Dataset) -> Mapping[Hashable, pyproj.CRS | np.
         trf = pyproj.Transformer.from_crs(wgs84, crs, always_xy=True)
         e, n = trf.transform(cen_lon, cen_lat)
 
-    nx = ds.sizes['west_east']
-    ny = ds.sizes['south_north']
+    nx = np.float64(ds.sizes['west_east'])
+    ny = np.float64(ds.sizes['south_north'])
     x0 = -(nx - 1) / 2.0 * dx + e  # DL corner
     y0 = -(ny - 1) / 2.0 * dy + n  # DL corner