(Raak) I don't have any figures but I would guess the answer is none. Every winter it goes down to at least -45° so the cold is part of the environment and everybody knows it, even pissed teenagers at a guess. Sudden blizzards and storminess are pretty well unknown. There is actually very little weather in winter except a persistent thin fog, largely produced, it seems, by the city itself (people breathing, car exhausts, hot cups of tea etc).