Sadly something like this doesn't exist internationally from what I can tell. I live in Japan and have no idea which sources are good and which are bad.
The local apps pull data from the Japan Meteorological Agency, so does Apple Weather, and so does Carrot Weather since a recent update (though those 2 still give me different results).
Outside of Japan, when I travel, I have no idea so I just leave the Carrot Weather source on Apple Weather, because that at least pulls data from local weather services if available (https://developer.apple.com/weatherkit/data-source-attributi...)
The local apps pull data from the Japan Meteorological Agency, so does Apple Weather, and so does Carrot Weather since a recent update (though those 2 still give me different results). Outside of Japan, when I travel, I have no idea so I just leave the Carrot Weather source on Apple Weather, because that at least pulls data from local weather services if available (https://developer.apple.com/weatherkit/data-source-attributi...)