You step through the door of the Charms classroom to find...

A winter wonderland.

Everything is ice-and-snow. There are ice ridges and little snow-capped hills and, in the centre, a large ice rink. The desks are arranged on this ice-rink in neat rows, with the Professor's desk set at the front. Given that the ice-rink is charmed for now, it shouldn't be hard to get to your desk. The moment you sit down, you notice that the weather isn't downright cold: it's cool and pleasant, but not bitter.

Professor Descoteaux is leaning against his desk, his posture graceful and just a little lazy.