On January 22, 1943, a frontal boundary separated cold Artic air from warm Pacific air over the Black Hills, causing drastic changes in temperature in the region. Spearfish, nestled in the higher elevations of the Northern Hills, experienced what remains the fastest recorded temperature change, as chronicled by the National Weather Service.
At 7:32 a.m., the temperature in Spearfish rose from -4 degrees Fahrenheit to 45 degrees in just two minutes. Two hours later, the temperature dove from a balmy 54 degrees to -4 degrees, resulting in a change of 58 degrees over 27 minutes. A similar event was experienced in nearby Rapid City. By 9:20 a.m., Rapid City was a crisp 5 degrees at 9:20 a.m. which warmed to 54 degrees by 9:40 a.m.
Locals are well aware that drastic changes in weather are not uncommon events in the Black Hills. The higher elevation of the Black Hills. Shifts in wind direction as well as inversions, which occur when warmer air settles over a body of cooler air, are responsible for the resulting weather peculiarities.