Air Date: Week of January 3, 2003

This week, we have facts about a Chinook Wind that swept through a South Dakota town, causing the fastest temperature change in history.

Transcript

CURWOOD: Welcome Back to Living on Earth. I’m Steve Curwood. Sixty years ago this month, residents of the town of Spearfish, South Dakota woke up to a thermal surprise. In just two minutes the temperature in Spearfish rocketed up 49 degrees. At seven-thirty in the morning of January 22, 1943 it was a bitterly cold minus four degrees. But by 7:32 it had jumped to a relatively balmy 45. The phenomenon is still in the record books as the fastest temperature change ever recorded.

Now for the why. Science points to the Chinook Wind. “Chinook” means “snow eater” in the language of some Native Americans, and this warm, dry wind certainly does eat up snow cover. Chinooks happen when warm air pours down a mountainside. In Spearfish, the dramatic Chinook came up over the Black Hills. Unique air currents caused wind from one side of the hills to heat up drastically as it descended into the cold air mass on the other side.

Despite respite from the cold, Chinook winds can create problems. The hot, dry air has been known to start wild fires and damage plants. Similar winds in the Alps have caused deadly avalanches. And the Chinooks can be cruelly unpredictable.

In Spearfish in 1943, the pleasant weather lasted only an hour, before the temperature dropped back to minus five degrees in less than 30 minutes. Car windshields cracked, and cattle and people alike were stunned, as the season seemed to change from winter to spring and back again, all before lunch. And for this week, that's the Living on Earth Almanac.

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