"My windshield wipers couldn't move fast enough. It was raining pretty hard. There was just so much water all over. I couldn't tell what was going on," said Eric McGinley, whose car got caught up in the flash-flooding near Gilman Springs.
McGinley said his visibility was so poor that he didn't realize he was driving into a massive mudslide. Firefighters say McGinley wasn't the only driver who was caught off guard by the powerful storm.
PHOTOS: Rain soaks Southern California
"At 1:30 this morning, approximately, we got our first call about a rescue. Since then, we've rescued 40 people out of their vehicles," said Capt. Lucas Spelman with the Riverside County Fire Department.
Tow truck driver Chris Lewis also said he had a busy day after having to dig out several cars. Lewis said the owner of one of the vehicles caught up in the flash-flooding told him the wall of mud "looked like the Universal Studios tour ride where the flood of water rushes down that village, but just mud."
Eight residents were evacuated from their homes as a precautionary measure in the 20500 block of Gilman Springs Road due to the threat of mud and debris flow. Firefighters also asked several residents on Soboba Road to evacuate their homes. No injuries were reported.
Sam Wait of Gilman Hot Springs said he had never seen such mounds of mud.
"It's like Mother Nature's way of saying, 'Hey, you live next to a mountain bro,'" said Wait.
The worst debris flow happened in front of the Golden Era Productions facility, which is part of the Church of Scientology.
Gilman Springs Road remains closed between Sanderson Avenue and State Street. Riverside County crews hope to have it open by Saturday afternoon. Soboba Road, too, remained obstructed between State and Chabela Drive, county officials said.
Heavy flooding also displaced two families from two apartments on the 41900 block of Acacia Avenue in Hemet.
VIDEO: Cars get caught in flash-flooding in Hemet
Tammy Gatavetsky's home was flooded, and all her valuables were damaged.
"We just finished paying our rent and all our bills. We have like $97 for the month to live on," said Gatavetsky.
Directly across the street, Sammy Ramirez was leaving for work when his car stalled in a driveway.
"It was terrible dude. It's never been this bad," said Ramirez.
The strong flow of water and debris is also being blamed for damaging a natural gas meter.
In San Jacinto, firefighters rescued three people trapped in a vehicle in water on Soboba Road near Lake Park Drive; the occupants of the vehicle were not injured.
A flash-flood warning for western Riverside County expired at 8:30 a.m. The rain moved southeast and was out of most areas by late Thursday morning.