On Monday afternoon, a line of severe thunderstorms blasted through central and southeastern North Dakota, producing very strong wind gusts in excess of 80 mph at many locations including Jamestown and the greater Fargo-Moorhead area. Some people were surprised at the storms' severity, given that the weather was so cool that day. The severe storm threat had actually been predicted starting Friday and was not a surprise to weather forecasters in the area.
Warm, humid and unstable air was notably absent at the surface, but was present in abundance above the surface layer. This is known as "elevated instability" and such cool-weather storms are known as "elevated convective storms."
In these situations, tornadoes are not as likely, but damaging wind gusts, hail and torrential rain can still happen even on a cool, September day, even if it doesn't feel like it will.