A Chinook is a wind that is generally warm and originates from the eastern slope of the Rocky Mountains. It often moves from the southwest in a downslope manner, causing a noticeable rise in temperature that helps to warm the plains just east of the Rocky Mountains.

The Chinook is classified as a katabatic wind. A katabatic wind develops because of cold, heavy air spilling down sloping terrain, moving the lighter, warmer air in front of it. The air is dried and heated as it streams down the slope. At times the falling air becomes warmer than the air it restores. Some katabatic winds have been interestingly named, like Taku, a frigid wind in Alaska, or Santa Ana, a warmer wind from the Sierras.