That’s a result of the weather site that’s being used. For whatever reason, it seems like they have certain ‘breakpoints’ at which they change the layout… but for whatever reason they don’t try to fill the full size of the window (or tile in this case).
While I think there’s probably something that could be done, I think you’re fighting an uphill battle at this point.
Have you tried the weather widgets in this thread:
It looks like OpenWeatherMap (the underlying weather data source for the custom tile) has weather data for your area https://openweathermap.org/city/293725