Chinooks occur when a mountain range is exposed to a strong winds blowing at right angles, or near right angles to the direction of the mountain ridge. Moist air is forced up the mountains bringing both cloud and precipitation to the windward side. The descending air then becomes warmer and drier as it is forced down the leeward side of the mountains. The relatively warm, dry gusty winds that occasionally occur to the leeward side of mountain ranges around the world are known by many names. In Canada and the northern United States, they are referred to as Chinooks. In the southern states, they are known as Santa Ana and in parts of Europe, foehn winds.