I really like Breezy Weather. You can remove elements you don't want and it seems to support rain notifications.

Breezy

https://f-droid.org/en/packages/org.breezyweather/

Breezy Weather (a fork of Geometric Weather) is an awesome option! Just of note, there are two versions. You have the "standard" version with all weather sources (on their own F-Droid repos, IzzyDroid, and directly through their Git repo) and the "free" version which removes non-free weather sources (on their own F-Droid repos, the official F-Droid repo, and their own Git repo)

So if you install it through the F-Droid repos, you will only have free weather sources (like Open-Meteo) while if you install through IzzyDroid it will include non-free weather sources. Using their own repos / their GitHub lets you pick between the two. Just something of note, in case you feel strongly for or against non-free weather sources.

Breezy Weather has a really clean UI and the information shown can be customised. If you don't want stuff like pressure or wind speed to be shown, you can disable it! You can toggle notifications for alerts, next day forecasts, etc. You can also change what weather sources you are using per location, e.g. if you have added Hong Kong you might want to use the HKO for alerts.

Has anyone recommended Breezy yet? It's great!

Breezy

The KNMI app is great and non commercial! It's made by the Dutch Meteorological Institute

Merry Sky FTW! I'm not sure if it sends alerts but it's simple and effective. I made it a phone app and I love it.