popcorn storm n. a brief, unexpected rain shower or thunderstorm. Also, collectively and more formally, popcorn convection. (source: Double-Tongued Dictionary)
Further reading
Thunderstorms might sound scary, but playful explanations for all those booms can help reassure little ones: How about the potato wagon’s rolling over the bridge? Or the angels are going bowling? Plus, if you just finished enjoying an...
There are lots of colloquial phrases to explain away the cacophony of a thunderstorm: The potato wagons are rolling, The tater wagon’s going over the bridge, The potato wagon broke down, and God is dumping out potatoes and washing them off. In...