Black Hills residents are no strangers to extreme weather, but the events of January 22, 1943 took even the most seasoned veterans by surprise. On that date, a dramatic temperature swing in Spearfish set a world record that stands to this day.
The Black Hills are often referred to as the “Banana Belt of the Midwest” due to their milder climate in contrast to the rest of South Dakota and the surrounding region. This is due to geography: the Hills act as a barrier against intrusions of cold arctic air from the north, sheltering communities on the lee side of the mountains from the worst of the cold and leading to frequent temperature inversions—layers of warmer air that overrun shallow pools of cold air at the surface. Additionally, warm, moist air from the Pacific Ocean cools as it collides with the Black Hills, wringing out moisture on the windward slopes. The dried air then picks up speed and warms as it races down the leeward slopes, leading to gusty winds known as Chinooks. Chinook winds can cause rapid changes in temperature, and that’s precisely what happened on the morning of January 22, 1943 in Spearfish and other towns on the east slopes of the Black Hills.
That morning, the temperature in Spearfish was a frigid -4º at 7:32 a.m. As a cold front moved northeast over the Black Hills, Chinook winds began blowing in earnest, causing the temperature to jump to an astounding 45º in just two minutes. This 49-degree temperature change was the most extreme ever recorded by the National Weather Service (and was later reported in Ripley’s Believe it or Not and other national media outlets). The temperature reached 54º by 9:00 a.m., but the rollercoaster ride wasn’t over quite yet. The Chinooks died down just as suddenly as they had appeared, and the temperature plunged 58 degrees, falling back down to -4º in 27 minutes. This caused plate glass windows and automobile windshields to frost over suddenly and crack due to the abrupt temperature change.
Other communities, including Sturgis and Rapid City, were similarly affected as temperatures fluctuated back and forth all day. The temperature in Rapid City rose 32º in four minutes beginning at 10:29 a.m., only to drop by 22º in three minutes starting at 10:36 a.m. Back and forth it went: 60º at 11:57 a.m., 13º at 12:02 p.m., 50º at 12:46 p.m., 58º at 5:22 p.m., 17º at 5:26 p.m. as a result of the cold front becoming quasi-stationary over western South Dakota, with Continental Arctic air to the north and Maritime Polar air to the north; subtle shifts in direction led to extreme temperature swings over incredibly short distances. The phenomenon caused streets to frost over immediately, only to melt moments later, making driving hazardous—if not impossible. At one point, the east side of the Hotel Alex Johnson resembled a winter wonderland while spring-like weather could be found just around the corner, on the south side. Temperatures in both Rapid City and Spearfish were recorded on Montana-Dakota Utilities Company thermometers in both towns.
Chinook winds continue to occur every winter in the Black Hills, but almost eight decades later, such drastic fluctuations in temperature have never been equaled. Spearfish actually embraces its notoriety; in 2019, it created a new winter festival called Chinook Days to celebrate its world record for the fastest/greatest temperature change. Naturally, it’s held on the weekend closest to January 22.
WORDS: MARK PETRUSKA