Apple Weather forecasts for my area have shown a 30-50% chance of precipitation for eternity, even when there isn’t a cloud in sight. My meteorologist has told his readers to ignore Apple’s forecasts.
This started around the time the Apple Weather outages a few months ago and haven’t improved. YSK that you can report inaccurate forecasts from within the app, but it hasn’t improved for me.
I’m currently using Foreca on iPhone and the free version of Carrot on Apple Watch.
The different models definitely do not produce the same output and some weather conditions are extremely difficult to predict with any accuracy (especially rain). Even the “current” conditions are often very different depending on the model since they rarely use actual observations… and even if they did the next city block over could be totally different).
Which one is the most accurate depends on your location (in particular, your latitude, proximity to the ocean, nearby mountains, etc).
Even little things like standing near (not even under) a tree can drastically alter your air temperature - because trees raise the humidity of the air around them and a slight humidity change has a drastic effect on temperature.
Apple most likely uses multiple models.
That’s why when they take air temperature samples they take multiple samples from multiple locations and they explicitly don’t put them under trees, behind shade, unusually high up.
If you’re standing under a tree resulting in a lower air temperature that won’t affect the weather prediction because the temperature isn’t taken from your phone.
Per apple it looks like for the US they use the weather channel.