The game will most likely have the mountain hood in perma snow. While the other hoods will be neutral or clear/sunny like others worlds are without seasons. Seasons will only add changing weather and actual seasons to the world so I'd imagine in winter the whole world would be snowy and in summer only the mountain hood would stay snowy.
As for snow activities "should/shouldn't" be tied to season I say shouldn't. If they add them, yeah great, but personally I prefer that they are being put into a seperate dedicated pack since I personally found the halfpipe for snowboarding in ts3 to be kinda a let down. With this we are getting actual snowboarding and skiing.
Also I like how ts4 seasons focused less on hot weather/cold weather activities and focused more on the holidays that you celebrate throughout the year. I found that ts3 holidays were pretty limited and over generalized.
