I personally use breezy weather after using many other free and open source weather apps before deciding on breezy weather as the best by a long shot.
Make sure to also get your weather info from a non-profit or government based weather institution, as commercial for-profit weather companies (AccuWeather especially) have done some insanely scummy things. They have previously (successfully) lobbied to prevent the US National Weather Service (NWS) from making a mobile app or making their website actually usable. They have also tried to lobby to make it so the US NWS could only give their weather info to commerical companies and not the everyday person or organization. Both of those things were done exclusively by AccuWeather, as they arent a good company by any stretch of the word. They have done way more scummy things in the past but this is not the place to be discussing all that as all you asked for is what weather app to use.
The weather source I personally use is the Norwegian Meteorological Institution (MET Norway), as it's a government service and free. It is also way more accurate than OpenWeather, at least for my location.