We have those all the time in AZ, mostly because of the heat, and we ignore those. But sometimes, I guess you should pay attention. Rode home today, cyclocross style through floods, in "scattered thunderstorms" that turned out to include hail the size of marbles. Shooters, not pee-wees.
It was fun, though, in an odd sort of way. Saw one other cyclist, and we laughed at each other as we passed, trying to stay on a bike path you couldn't see.