Well Bruma certainly would ever be lush and blooming, but still maybe like a little snow over the grass in warmer seasons...
Bruma is high up in the mountains, far away from water. That makes for a pretty cold climate. Many parts of Skyrim, although further north, might have more temperate climates.
I'm from Norway, considered a pretty cold country. The summers can still get pretty hot, even all the way up north in Finnmark, which is the northernmost part of the country. So I don't see why there is a need for permafrost in EVERY part of Skyrim, although there will probably be in many areas.
My guess is they'll do something like Morrowind and create a diversity, even though it might contradictory to what's said in lore previously. An entire game-world covered in snow all the time would be too boring. I'm sure there will be plenty of diversity.