I think they were doing some magic with the Android phone sensors, large amounts of user reports, as well as the actual forecast models.
Before Apple bought them, my Android phone was its own party trick at the bar. I'd be able to tell people down to the minute when it would start and stop raining. It was amazing for bar hopping on bad weather days.
What the actual crap did Apple do to mess it up so bad then?
Switching between providers on Carrot, Apple Weather often doesn't predict any amount of rain for the entire week, meanwhile I'm soaked in water in a thunderstorm, and NOAA and others predicted rain the entire week (which it did).
Before Apple bought them, my Android phone was its own party trick at the bar. I'd be able to tell people down to the minute when it would start and stop raining. It was amazing for bar hopping on bad weather days.