The Great Blue Norther of 1873 was the coldest temperature drop in US history - Apparently.
On December 10, 1873, the town of Sherman, Texas, recorded a temperature drop of 103°F (58°C) in just 24 hours, from 68°F (20°C) to -35°F (-37°C). This extreme temperature fluctuation is still the largest recorded in US history, and it remains one of the most remarkable weather events in the country's climate history. The event was documented by the local newspaper, and the temperature readings were later verified by the US Weather Bureau.