Residents in Spearfish, S.D. on Jan. 22, 1943 had two hours to remember. The day began with a chilly -4 reading at 7:30 a.m. However, two minutes later, the thermometer read 45 degrees -- a 49 degree jump!
The temperature then slowly warmed to 54 degrees around 9 a.m., before -- get this -- dropping 58 degrees over the next 27 minutes, to where they were back to a -4 reading by 9:27 a.m. Those who overslept must have thought the weatherman was crazy to say the high temperature for the day was 54.
It was likely due to cold and warm air sloshing back and forth along the flat plains at the base of the nearby mountains.