Severe weather is not at all unusual during the summer over Southern California. However, most of us don’t experience it because it happens mostly over the mountains and deserts.
It’s a seasonal occurrence when the winds shift and approach us from the south or the southeast.
Here’s a sample of what you’ll find on the link from the National Weather Service.
“1959: An intense thunderstorm hit east of Joshua Tree City between noon and 1 pm. Heavy debris flows came from the canyons and damaged numerous homes. Sand more than three feet deep covered some properties.”