Playground slides.
Each team gets a long strip of snow-covered tarmac and has to turn it into the longest possible slide by running at it and skidding in school shoes. Points are awarded for length and style, e.g. one-footed, piggyback, "the Diddyman", etc.
After 1 hour, a sour-faced caretaker turns up with a bucket of rock salt and tells the competitors to do something more useful with their lives.