You havent specified what phone OS you are using (iOS or Android) but 1st step is to make sure location in your PHONE is always on.
2nd - The information seems to be drawn from a phone's Accuweather app, so install that on your phone. The phone app is available for both operating systems in their respective app stores.
3rd- Be aware that the location you are in when you set this up becomes the primary location whose name & temperature values appear appear on the Fitbit tile and any clock faces that show that info. While you can add a maximum of two additional locations after it is working, you may not be able to delete that initial one.
