Afternoon Thunderstorm Season Strikes

Jul 30, 2020

Afternoon thunderstorm season starts in Wyoming in July.
Credit Matthias Krumbholz

Afternoon thunderstorms tend to happen in July and August across the mountain west. University of Wyoming Atmospheric Scientist Karen Kosiba said that's because it's monsoon season.

In the summer, the ground heats up from the sun in the morning. When the heat rises, this creates a channel for air to move upward. This upward flow and the extra moisture in the air help to create afternoon thunderstorms, Kosiba said.

"What starts happening in July and August is you get what we call the monsoon flow, where the atmosphere sets up a pattern that funnels moisture," she said. "This abundance of moisture that isn't usually there during a lot of the season coupled with the terrain that it's coming through makes afternoon storms a thing that starts happening."

Kosiba said that hailstorms form in a similar way but with something extra.

"In order to get hail occurring with these storms, you need a little bit more going on in the atmosphere," said Kosiba. "When that happens you're able to get these really big strong updrafts. If part of that updraft is above freezing level, then you start getting hail forming."

Next time you get caught in an afternoon storm, take a second to appreciate all the factors that went into forming it as you run to your car.

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