diff --git a/climax/main/preprocess.py b/climax/main/preprocess.py
index 23bce1afc9252b381435b400590ec1ef11b4056e..602c6cb1bda7d310a0a44d30e68cc60b78bdb756 100644
--- a/climax/main/preprocess.py
+++ b/climax/main/preprocess.py
@@ -174,7 +174,7 @@ if __name__ == '__main__':
                     ['{}'.format(file) for file in group]))
 
                 # read multiple netcdf files using xarray and dask
-                ds = xr.open_mfdataset(group).load()
+                ds = xr.open_mfdataset(group, parallel=True).compute()
 
                 # save aggregated netcdf file
                 LOGGER.info('Saving aggregated NetCDF: {}'.format(filename))