As spin said, taking finding shelter in a real thunderstorm is always the wisest thing to do. With experience and simple observation, you get good at judging time left before out hits and spotting good shelter areas.
Where are you? Mississippi, France? Australia?
I ask because in this part of Canada it's been pretty rainy lately, more flooding than other years, but summer storms in this part of eastern Canada tend to be short lived, and usually rare to have actual days of rain-- but it depends where you are.
Too late for you perhaps, but having full rain gear, rain jacket, pants and booties, makes ALL the difference, cuz at least everything isn't soaked for days.
This has made it a lot easier with dealing with bad weather and just soldiering on.