It's pure talent, basically, and amongst my MANY great qualities and capabilities where wizarding is concerned, weather prediction is one of them.
It's going to SNOW!!!!
Just kidding I can't really predict the weather like that. I mean, I could, but it'd be a whole load of effort and all I really had to do was look out my window and see snow flakes. STILL. How VERY EXCITING!!! SNOW! WHO WANTS TO PLAY?