We haven't even seen raid yet -sniff-
I hope rain is in. And if it's in, I hope like this: http://www.youtube.com/watch?v=mHoSMFSksFg
P.S: If dynamic snow is dynamic, I'm pretty sure, almost confident, it's dynamic everywhere. It's probably a lot harder to just make it dynamic of certain types of objects. Look at the end of the trailer. The dragon's crash removes the snow from the ground. So does the dragon's fire in the start.
@joshw873: Rain and snow falling through meshes is probably the absolutely easiest thing to get rid of. Should be zero problem whatsoever, and should have been at Oblivion's time as well.