ACTON, Calif. — A Southern California desert community was cleaning up Friday after thunderstorms unleashed muddy torrents through streets and homes, threatened a commuter rail line and forced rescues of trapped motorists.

The downpours struck Thursday afternoon north of Los Angeles in semi-rural Acton as monsoonal flow of extremely moist air streaming across the region boiled up into huge thunderheads.

One man trapped in a pickup truck surrounded by an instant river of muddy water had to be hoisted to safety by a helicopter crew. In all, 14 people were rescued by fire crews, the Los Angeles County Fire Department said.

One flood swept through Hillary Mulligan’s home.

“It’s a mess,” she told KABC-TV (http://abc7.com/ ). “There was nothing you could do, like you couldn’t stop it.”

David Collupy was recording video of hail falling when the violent storm toppled a tree outside his home.

“I just couldn’t believe — it was like a monsoon rolled in, a really freak storm,” he told the station.

A 53 mph (85 kph) wind gust was recorded at nearby Lake Palmdale during the thunderstorms, the National Weather Service said.

A Metrolink commuter train on a run between Los Angeles and the high desert Antelope Valley was forced to stop as rushing water chewed away at an earthen embankment underneath the tracks.

Metrolink reported train cancellations and delays during the Friday morning commute.

The deluge was the latest from a week of hot and very humid weather as moisture-laden air flowed from east to west across Southern California, hurling lightning bolts and forming massive clouds.

Most of the flash floods occurred in inland mountain and desert areas. But some of the effects reached all the way to the coast. On Tuesday, the threat of lightning forced the evacuation of thousands of people attending the Vans U.S. Open of Surfing at Huntington Beach.

On Friday, Southern California was free of storm watches and warnings for the first time in days as southwesterly flow brought in drier and more stable air.

The National Weather Service said, however, that a slight chance of thunderstorms remained for the mountain ranges east of Los Angeles.