diff --git a/src/metpy/io/station_data.py b/src/metpy/io/station_data.py
index 4db0f2ec5e1..df7e153b5bf 100644
--- a/src/metpy/io/station_data.py
+++ b/src/metpy/io/station_data.py
@@ -191,8 +191,9 @@ def key_finder(df):
         raise KeyError('Second argument not provided to add_station_lat_lon, but none of '
                        f'{names_to_try} were found.')
 
-    df['latitude'] = None
-    df['longitude'] = None
+    df['latitude'] = np.nan
+    df['longitude'] = np.nan
+
     if stn_var is None:
         stn_var = key_finder(df)
     for stn in df[stn_var].unique():
diff --git a/tests/io/test_station_data.py b/tests/io/test_station_data.py
index 7e0e9b0d703..a281ad830d2 100644
--- a/tests/io/test_station_data.py
+++ b/tests/io/test_station_data.py
@@ -23,6 +23,7 @@ def test_add_lat_lon_station_data():
     assert_almost_equal(df.loc[df.station == 'KDEN'].longitude.values[0], -104.65)
     assert_almost_equal(df.loc[df.station == 'PAAA'].latitude.values[0], np.nan)
     assert_almost_equal(df.loc[df.station == 'PAAA'].longitude.values[0], np.nan)
+    assert df['longitude'].dtype == np.float64
 
 
 def test_add_lat_lon_station_data_optional():