Dear Tom,

In school we just read the book “The Little House on the Prairie.” In it, there were references to a Chinook wind. What is that?

Sally Koehn

Dear Sally,

The Chinook wind is a downsloping warm, dry wind, which sinks out of the Rockies. It is often referred to as a “snow-eater”, producing temperature jumps as much as 36 degrees in an hour and it can melt a foot of snow in a day. An extreme case of a Chinook wind occurred Jan.22, 1943 at Spearfish, SD where the temperature jumped from -4 degrees to +49 degrees in two minutes. Chinooks have been known to roar out of the mountains at high speeds, at times, in excess of 100 mph, not only raising temperatures, but dropping the humidity to less than 5%. The presence of mountains is essential. The movement of air from high altitudes to denser, low-altitude air is responsible for producing the compressional warming at the heart of the Chinook effect.