Edit: I suspect it's the Windy.app one. My initial impression is it looks quite nice. Available on both iOS and Android.
Came here, like I come to every weather API/tool discussion, to ask the same thing ... I would really like a less spammy, less bloated 10-day forecast a la WU.
This comes close, however - there's a nice 7-day lookahead ... is it possible that WU is just fudging days 8-9-10 and no real data is available beyond 7 days ?
Another method that's occasionally used is to just fill in with TMY (Typical Meteorological Year) data. Lots of those data sets are freely available, or if not, are very inexpensive to calculate if station data is available.
If you're looking for a minimally spammy, information dense forecast and you're in the US, it's pretty hard to beat weather.gov. (And make sure to occasionally read the zone and regional forecast discussion texts, too. They're really interesting and often educational!)
A while back I installed quite a few weather apps on Android, at the time, I felt wX and QuickWeather (from F-Droid) were the best. Maybe Flowx will be even better :-)
Link: https://weathergraph.app
Screenshots: https://impresskit.net/6430c7f0-b34b-418f-9824-f386f939be9a/...
What do you think?