Chinook, warm, dry, westerly wind occurring in winter and spring on the Rocky Mountain eastern slopes. Pacific air condensing moisture on the mountains' western slopes result in air that increases in temperature 1 °F for every 180ft (1°C for every 99 m) as it descends the eastern slope. Chinooks, called snow eaters, rapidly melt and evaporate ground snow. The wind was named by settlers who thought it came from the direction of the Chinook Indian camp along the Columbia River. Similar winds blowing elsewhere are called foehns.