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Radical record temperature rise

The greatest temperature swing ever recorded in North America occurred in Spearfish, South Dakota on January 22, 1943. The temperature at 7:30 a.m. was –4°F. Two minutes later, the temperature had risen to 45°F, the fastest warmup ever recorded in the U.S. By 8:45 a.m., the temp reached 55°F — before plummeting back to 0°F 45 minutes later. A recording thermometer at the Montana-Dakota Utilities building documented the event for history. On the left is the original thermograph, and on the right is the temperature data on a flat graph for easier viewing

Spearfish thermographTemperature rise graph
Images courtesy Dr. Dennis Todey, SDSU

Here is the way the event was reported in the Spearfish Queen City Mail: "[Tommy] Thompson said the IOOF building immediately turned white with frost. Car windows iced up, and drivers had to stop in the middle of the street because they couldn't see. By the time Thompson arrived at work, a crowd was gathering in front of the MDU office to watch the thermometer. Marion Vaughn was working as cashier at MDU. She said, 'People crowded the window all the day and there was lots of excitement. Finally we took the recording and laid it down in the window so people could see it easier. It was really a phenomenon, almost eerie. People couldn't understand it.'"

The fluctuating temperatures damaged many pine trees in the Spearfish area. The Guinness Book of World Records called the Spearfish episode the "world's greatest variance in temperature." But the pool of hot air also invaded other nearby places. According to Black Hills Believables, "At mid-morning downtown, Rapid City's temperature was near zero, while the Canyon Lake neighborhood basked in 55 degrees. Motorists crossing from the ice box zone to a warmer part of town were forced to pull over, their windshields instantly obscured by peculiar frost. Here's what the Rapid City Journal said the next day: "The phenomenon was striking at the Alex Johnson Hotel corner at 11 a.m. On the east side of the hotel, winter was in all its glory, biting legs and faces, while around the corner on the south side, not fifty feet away, spring held sway."

A lot of places around the country claim their weather is capable of changing from minute to minute. In the Black Hills, they can prove it.

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