Michael Ritter / AP A tornado touches down in Riverside on Thursday, during a wild weather system that lashed Southern California with fierce thunderstorms that unleashed mudslides in wildfire-scarred canyons and dusted mountains and communities with snow and hail. May 22, 2008. A wild weather system lashed Southern California on Thursday with fierce thunderstorms that unleashed mudslides in wildfire-scarred canyons, spawned at least one tornado and dusted mountains and even low-lying communities with snow and hail.

SANTA ANA — A wild weather system lashed Southern California on Thursday with fierce thunderstorms that unleashed mudslides in wildfire-scarred canyons, spawned a tornado and dusted mountains and even low-lying communities with snow and hail.

The National Weather Service issued tornado warnings for parts of Riverside County about 55 miles east of Los Angeles, and area residents flooded TV stations with pictures and video of funnel clouds and at least one tornado on the ground.

Powerful wind or a funnel cloud toppled a tractor-trailer on a highway and freight cars on nearby railroad tracks, said Riverside County fire spokeswoman Jody Hageman. One person was rescued from the wrecked truck.

"It got real windy, the sky got real dark," said James Smith, a manager at a fitness center at nearby March Air Reserve Base. He was not aware of any damage to the base.

Michael Ritter was scrambling to put away lawn furniture in his backyard in Riverside when he spotted a tornado and grabbed his camera.

"It looked like one of those dirt devils and then it got bigger. I've never seen anything remotely as big," Ritter said. "We could hear the wind from a mile away and see the debris flying up. I thought, that's the real thing."

Earlier in the day mud flows swept down canyons in neighboring Orange County.

Evacuation orders were issued to about 1,500 people in Williams, Modjeska and Trabuco canyons, areas devastated by a 28,000-acre wildfire last fall, said Orange County Fire Authority Capt. Mike Blawn.

A handful of residents at the top of Williams Canyon were temporarily stranded, fire officials said.

Aerial TV footage showed thick layers of mud surrounding homes as residents picked their way outside and began to clear properties with shovels. A road in Trabuco Canyon was impassable.

It was not known how many complied with the evacuation orders, which were lifted after a few hours.

April Brown, who runs a propane store in Modjeska Canyon with her husband, said she watched a creek swell during a half-hour downpour.

"You could just hear the boulders in the creek moving and popping and crashing into each other," Brown said. "I saw trees going down the creek."

The National Weather Service issued numerous flash-flood warnings through the day as thunderstorms pushed across the state's southern counties, from metropolitan Los Angeles south to central San Diego County and eastward through Riverside and San Bernardino counties.

Localized street and freeway flooding swamped cars and jammed traffic around the region.

A layer of hail coated parts of Baldwin Park, a San Gabriel Valley suburb east of Los Angeles.

"It's amazing," said Kela Carbajal, a hairdresser at the Olive Square Barber Shop. "The kids go around grabbing at the snow and throwing it at cars."

Lightning sparked many brush fires in northern and eastern San Diego County but they were quickly doused, said Nick Schuler, a spokesman for the California Department of Forestry and Fire Protection.

In Santa Barbara County, firefighters kept watch on the weather and the potential for lightning, county fire Capt. Eli Iskow said.

"Our fuels are already dried out, primed and ready to burn, so even with a little moisture in the air, they're still going to burn," he said.

Residents of the San Bernardino Mountains communities northeast of Los Angeles awakened to snow-dusted peaks, and hailstorms peppered parts of the region. Quarter-inch hail fell as a huge thunderstorm blew through Ramona in San Diego County, said local airport worker David Boone.

Unusually cold late-season weather wasn't limited to Southern California, which just last weekend baked in 100-degree highs.

In the Sierra, about 2.5 inches of snow fell overnight in the Mammoth Lakes area, and as much as six inches of snow fell in upper elevations there, said Scott McGuire, a meteorologist with the National Weather Service in Reno.

Southern California forecasts indicated rain and thunderstorms, and cooler-than-normal temperatures would continue into Memorial Day weekend.