I use Windy, it's meant for boating, but it's really useful for me at work (stonemason) because rain isn't great for fresh mortar, wind driven rain is even worse, and if it's too windy to climb up the scaffolding I'd like a heads up.

Edit: The free version is somewhat limited, but I haven't bought a license and still find it really useful.

I personally use Weawow currently, but I used Windy before.

I use Rainy Days for the radar, and - since I'm in the UK - the Met Office weather app, which has a Next Rain widget.

I use/like "Radar Scope" it is a radar, not forecasting app.

I've been enjoying Ventusky for planning for rain gear when cycling. It's been good so far.