Five years ago today, it was 97 degrees in Fargo-Moorhead. That temperature broke the daily record high by 12 degrees. It also broke the October record high by four degrees and is the warmest temperature on record for so late in the year. The hot day was caused by the dynamics of the atmosphere that Sunday afternoon. At 1 p.m., the temperature had warmed to 81 degrees with a dew point of 47, and the day was on track to produce a record high around 87 as expected.
Then high pressure in the upper atmosphere created a surge of downward air ahead of a cold front. As this air sank, the increasing weight of the air above caused it to warm up and dry out. At 4 p.m. Sunday, the temperature was 97 degrees with a dew point of 36 which created a relative humidity of 12%; desert air at its finest.