Microsoft Weather comes out on top

Being a weather freak I check the accuracy of weather apps with Forecast Advisor. Much to my surprise Microsoft Weather comes out on top. For the year 2025, at my location, Microsoft Weather has an accuracy rating of 85.99% followed by The Weather Channel at 81.55%. For the month of December Microsoft comes out on top with a rating of 86.67%.

I wonder what is the source of their data.