diff --git a/src/weathergen/datasets/data_reader_base.py b/src/weathergen/datasets/data_reader_base.py
index 281a8c1db..bdf0d3641 100644
--- a/src/weathergen/datasets/data_reader_base.py
+++ b/src/weathergen/datasets/data_reader_base.py
@@ -475,6 +475,82 @@ def normalize_coords(self, coords: NDArray[DType]) -> NDArray[DType]:
 
         return coords
 
+    def _normalize(
+        self,
+        data: NDArray[DType],
+        idx: list[int],
+        mean: dict[int, float],
+        stdev: dict[int, float],
+        name: str,
+    ) -> NDArray[DType]:
+        """
+        Helper function to normalize data
+
+        Parameters
+        ----------
+        data :
+            data to be normalized
+        idx :
+            indices of channels to be normalized
+        mean :
+            mean values for channels
+        stdev :
+            standard deviation values for channels
+        name :
+            name of the data (for error messages)
+
+        Returns
+        -------
+        Normalized data
+        """
+        # assert data.shape[-1] == len(idx), f"incorrect number of {name} channels"
+        if data.shape[-1] != len(idx):
+            raise ValueError(
+                f"incorrect number of {name} channels: expected {len(idx)}, got {data.shape[-1]}"
+            )
+        for i, ch in enumerate(idx):
+            data[..., i] = (data[..., i] - mean[ch]) / stdev[ch]
+
+        return data
+
+    def _denormalize(
+        self,
+        data: NDArray[DType],
+        idx: list[int],
+        mean: dict[int, float],
+        stdev: dict[int, float],
+        name: str,
+    ) -> NDArray[DType]:
+        """
+        Helper function to denormalize data
+
+        Parameters
+        ----------
+        data :
+            data to be denormalized
+        idx :
+            indices of channels to be denormalized
+        mean :
+            mean values for channels
+        stdev :
+            standard deviation values for channels
+        name :
+            name of the data (for error messages)
+
+        Returns
+        -------
+        Denormalized data
+        """
+        # assert data.shape[-1] == len(idx), f"incorrect number of {name} channels"
+        if data.shape[-1] != len(idx):
+            raise ValueError(
+                f"incorrect number of {name} channels: expected {len(idx)}, got {data.shape[-1]}"
+            )
+        for i, ch in enumerate(idx):
+            data[..., i] = (data[..., i] * stdev[ch]) + mean[ch]
+
+        return data
+
     def normalize_geoinfos(self, geoinfos: NDArray[DType]) -> NDArray[DType]:
         """
         Normalize geoinfos
@@ -501,18 +577,14 @@ def normalize_source_channels(self, source: NDArray[DType]) -> NDArray[DType]:
 
         Parameters
         ----------
-        data :
+        source :
             data to be normalized
 
         Returns
         -------
-        Normalized data
+        Normalized source data
         """
-        assert source.shape[-1] == len(self.source_idx), "incorrect number of source channels"
-        for i, ch in enumerate(self.source_idx):
-            source[..., i] = (source[..., i] - self.mean[ch]) / self.stdev[ch]
-
-        return source
+        return self._normalize(source, self.source_idx, self.mean, self.stdev, "source")
 
     def normalize_target_channels(self, target: NDArray[DType]) -> NDArray[DType]:
         """
@@ -520,18 +592,14 @@ def normalize_target_channels(self, target: NDArray[DType]) -> NDArray[DType]:
 
         Parameters
         ----------
-        data :
+        target :
             data to be normalized
 
         Returns
         -------
-        Normalized data
+        Normalized target data
         """
-        assert target.shape[-1] == len(self.target_idx), "incorrect number of target channels"
-        for i, ch in enumerate(self.target_idx):
-            target[..., i] = (target[..., i] - self.mean[ch]) / self.stdev[ch]
-
-        return target
+        return self._normalize(target, self.target_idx, self.mean, self.stdev, "target")
 
     def denormalize_source_channels(self, source: NDArray[DType]) -> NDArray[DType]:
         """
@@ -539,37 +607,29 @@ def denormalize_source_channels(self, source: NDArray[DType]) -> NDArray[DType]:
 
         Parameters
         ----------
-        data :
+        source :
             data to be denormalized
 
         Returns
         -------
-        Denormalized data
+        Denormalized source data
         """
-        assert source.shape[-1] == len(self.source_idx), "incorrect number of source channels"
-        for i, ch in enumerate(self.source_idx):
-            source[..., i] = (source[..., i] * self.stdev[ch]) + self.mean[ch]
+        return self._denormalize(source, self.source_idx, self.mean, self.stdev, "source")
 
-        return source
-
-    def denormalize_target_channels(self, data: NDArray[DType]) -> NDArray[DType]:
+    def denormalize_target_channels(self, target: NDArray[DType]) -> NDArray[DType]:
         """
         Denormalize target channels
 
         Parameters
         ----------
-        data :
+        target :
             data to be denormalized (target or pred)
 
         Returns
         -------
-        Denormalized data
+        Denormalized target data
         """
-        assert data.shape[-1] == len(self.target_idx), "incorrect number of target channels"
-        for i, ch in enumerate(self.target_idx):
-            data[..., i] = (data[..., i] * self.stdev[ch]) + self.mean[ch]
-
-        return data
+        return self._denormalize(target, self.target_idx, self.mean, self.stdev, "target")
 
 
 class DataReaderTimestep(DataReaderBase):