Rescuers rushed into action in the Coachella Valley. Firefighters in Indio pulled a little girl from a car stranded by the quick-rising water.
The strong cells suddenly flooded much of the area. Workers at one gas station that was submerged say it all happened in an instant.
"It just came out of nowhere," said employee Brittney Ortega. "The inside of our ceiling broke, so our entire store is flooded."
Throughout the Coachella Valley, streets and intersections were flooded, creating dangerous conditions for drivers.
Jeffrey Briney of Laguana Beach captured video of a semi being swept away along Highway 95 near the Arizona border. He and his family were caught in a raging flash flood.
"We've only seen it on some of the crazy videos or on TV, and once we saw how strong the water was running, my wife and I were kind of freaking out with the kids in the car," he said.
Officials say there numerous rescues all across the area, but there has been no word of any serious injuries, and no word on the extent of the damage.
Part of a major rail line has been washed out near Needles. Emergency crews are working to repair the damage. Southern California Edison says residents in some areas may not have power fully restored until late Tuesday afternoon.