OSS Weather: An open source weather app for iOS/Android
iOS App: https://apps.apple.com/fr/app/oss-weather/id1499117252
Android App: https://play.google.com/store/apps/details?id=com.akylas.weather
Source Code: https://github.com/Akylas/oss-weather
I’m quite happy with:
Tiny Weather Forecast Germany (Weather forecast based on open data from the Deutscher Wetterdienst.) https://f-droid.org/packages/de.kaffeemitkoffein.tinyweatherforecastgermany/
It has nice widgets.