Chinook, << shih NOOK, >> is a warm dry wind that blows down the eastern slopes of the Rocky Mountains, usually in winter and early spring. It was named by early settlers who thought it came from the country of the Chinook Indians along the Columbia River. Chinooks blow in the Northwestern United States and in southwestern Canada. They usually blow from the west.
A chinook gets warmer as it moves down the mountain slope. Its temperature increases by about 1 degree Fahrenheit for every 180 feet (1 degree Celsius for every 99 meters) of descent. For example, a chinook that descends 5,500 feet (1,680 meters) is about 30 °F (17 °C) warmer when it reaches the foot of the mountain. The dry wind takes up moisture by evaporation. It often rapidly melts and evaporates snow as it spreads out at the mountain base. For this reason, chinooks are sometimes called snow eaters. Similar winds that blow in other parts of the world are called foehns (see Foehn ).
Residents along the Pacific Coast in Washington and Oregon use the name wet chinook for warm, moist winds that blow from the southwest.
