I use Flowx, it's customisability and access to so many excellent weather predictive models please me greatly.

Oh meine Kleine Wettervorschau

I use WTForecast. It's funny. I guess I technically also use the default Android weather app, because my lock screen has rain or snow on it when either is happening outside, it's kinda neat.

I switch weather apps a lot. Actually "clima" and "Bura" are really good. Clima has a simple design and Bura looks nice with some fancy graphs.