A "heat burst" is a rare weather phenomenon

"A rare weather phenomena known as a heat burst occurred in a remote area of northwest Minnesota before sunrise Thursday. 

At an automated weather station near the town of Fertile, Minn., the temperature rapidly rose from about 72 degrees at 3 a.m. to 93 degrees at 3:40 a.m. At the same time, the dewpoint went from the upper 60s to the low 40s — a staggering drop before normalizing back into the 60s."

Just 10 miles south, at the weather station in Waukon, Minn., the heat burst didn't occur. While it was 93 in Fertile, the temp stayed in the low 70s in Waukon.  

This from Wikipedia: 

In meteorology, a heat burst is a rare atmospheric phenomenon characterized by a sudden, localized increase in air temperature near the Earth's surface. Heat bursts typically occur during night-time and are associated with decaying thunderstorms. They are also characterized by extremely dry air and are sometimes associated with very strong, even damaging, winds.

Although the phenomenon is not fully understood, the event is thought to occur when rain evaporates (virga) into a parcel of cold, dry air high in the atmosphere, making the air denser than its surroundings. The parcel descends rapidly, warming due to compression, overshoots its equilibrium level, and reaches the surface, similar to a downburst.

It would be scary to be outdoors while this is happening.  You learn something every day.