A surprise storm lashed San Diego County with rain and snow, stranding as many as 500 motorists on a mountain freeway and pouring mud down onto another roadway but causing no major damage or injuries.
The weather was expected to clear Friday.
A 27-mile stretch of Interstate 8, which runs through the mountains in the eastern county and is a main artery from California into Arizona, was reopened before dawn Friday following a 12-hour shutdown.
The California Highway Patrol began escorting cars through, although big-rig trucks still were not allowed. The freeway was closed shortly after 4 p.m. Thursday when blowing snow and ice made the roadway impassable.
"It was just a big dump of snow, real fast," accompanied by high winds, California Highway Patrol Officer Jim Bettencourt said.
Cars spun out and hundreds of motorists were stopped in their tracks.
"I've been here for a while and trying to get around, but there's no going around, so you just have to be patient," stranded motorist Patty Kresin told KNSD-TV in San Diego.
Search-and-rescue teams went car to car. At least 30 people were taken to temporary shelters at a fire station and a casino nearby, according to the California Department of Forestry and Fire Protection.
By early Friday, authorities were pretty sure they had found all the stranded motorists, but teams were still checking for cars that might have gone over the side of the road, Bettencourt said.
The abandoned cars hampered snow plows.
"Now we have a virtual parking lot of empty vehicles," Bettencourt said. "You've got big rigs that are jackknifed. So it's going to be a pretty daunting task."
The unexpectedly severe weather snarled other roadways. Authorities reported 179 crashes on county roads between midnight and 9 p.m. Thursday, compared to the usual figure of 50 to 75 crashes in a typical day.
Authorities also shut down an 8-mile stretch of road between Poway and Ramona because of mudslides. About 2 feet of mud and rocks slid onto the highway after heavy rain fell in an area burned by last fall's wildfires.
The stormy weather was caused by a low-pressure system that originated in the Gulf of Alaska and unexpectedly moved into Southern California.
Rain, hail and snow also fell in the desert near Palm Springs where temperatures had soared to 85 degrees just days ago.