I've never had a problem in winter maps. Maybe a slight FPS tank during blizzards, but I've never had anyone DC or other such nonsense. If your computer can handle summer maps, it should handle blizzards; otherwise, maybe it's just time to upgrade.
This is pretty clearly not the case. Some people's computers can handle CoH 2 pretty well except when a blizzard hits. There's a clear performance drop that makes the game unplayable for some people.