The temperature in Fargo-Moorhead on Monday afternoon, June 1, reached 97 degrees, breaking the daily record high of 93 degrees set in 1933. Grand Forks also broke a record by a degree, reaching 94.
The afternoon temperature spike was forecast by no one, even earlier that afternoon. A process called "compressional heating" was responsible for the high numbers and also for fooling the weather models as well as the human forecasters.
A cold front was approaching, pushing dry air into the area. Dry air is denser and heavier than humid air, and the incoming dry air compressed the air we had in place, causing it to heat up. The temperature rose at an unusual pace, around 3 degrees per hour, during the midafternoon when the air temperature is usually fairly steady. Phone apps, which use modeled data for current conditions, were fooled as well, wrongly assumed the freak temperature rise would continue, and so were caught displaying false "current" temperatures near 100 degrees.