In Calgary and SW Alberta, there's a wind (or maybe more like a mass of warm air) which comes over the Rockies and warms the place up in the dead of winter. It was +20C on Christmas there one year. It's called a "Chinook" which is, I believe, a Native word. When the chinook comes, it pushes the clouds back in the sky and this is called a chinook arch. (Here's a great photo: http://www.nucleus.com/~cowboy/Misc/Chinooks.html)