Drivers trapped in cars as flash floods, mudslides hit Calif.

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Southern California authorities scrambled to rescue motorists stranded on roadways as flash floods and large hail pounded areas north of Los Angeles.

Flash floods sent water flowing into roads Thursday, triggering mudslides that forced the closure of a portion of Interstate 5.

Some motorists fled, while others sat trapped in cars and called 911 for help, according to Lisa Williams of the Los Angeles County Emergency Management.

Cars sat submerged in mud with their roofs barely visible. Hail the size of golf balls tumbled from the sky.

"It's possible that someone could have lived in SoCal all of their lives and never have seen this size hail," said Joe Sirard, a meteorologist with the National Weather Service.

"If this area does see hail, it is the size of a dime," Sirard said. "Definitely no bigger than a quarter."

While rain is common in winter, the amount that fell is rare for October, he said.

Between 4-6 inches of rain fell in parts of Kern and Los Angeles counties, prompting floods that led to nearly a half dozen water rescues.

"The area is hilly along with canyons ... so the mud was created by the runoff ... and the debris flowing downhill," he said.

It's unclear how many people are stuck on highways.

Firefighters are trying to account for people stuck in vehicles and searching for those who may need help getting to a safe area, said Humberto Agurcia, a spokesman for the Los Angeles County Fire Department.

Searches are focused on the Lake Hughes vicinity and surrounding areas.

The Lake Hughes area is mostly rural and it's unclear if there are people stuck in homes. Rescuers said most calls for help have come from trapped drivers.

There have been no reports of injuries so far, authorities said.