SAN FRANCISCO -- California remained under threat of mudslides and blizzards Thursday from the last in a weeklong series of storms that caused deadly accidents, churning seas and widespread flooding concerns.

Heavy rain was forecast Thursday in the San Francisco Bay Area and the National Weather Service said blizzards and even avalanches were a possibility in the higher elevations of the Sierra Nevada, where winds could gust to 125 mph (201 kph) on ridgetops.

"This is a life-threatening situation," the weather service warned.

Wednesday saw toppled trees, snarled roads and downed power lines all around Northern California, sometimes with deadly consequences.

A homeless man who may have been trying to shelter under some trees near an Oakland freeway was killed when the tree toppled and he was crushed by a 30-foot-long (9-meter) branch, authorities said.

The man may have been "just trying to stay dry," California Highway Patrol Officer Herman Baza said. "Unfortunately, that protection was deadly."

In Napa County, one person died when a car went out of control on a wet roadway and struck another vehicle, the California Highway Patrol said.

Tens of thousands of people were without electricity in Pacific Gas & electric areas, including more than 15,000 in San Jose alone late Wednesday night.

The weather service issued a high surf warning for San Francisco County through Friday, with 30-foot breakers along the coast of the North Bay, Monterey Bay and Big Sur.

Weather concerns also kept a stretch of scenic Highway 1 in Big Sur closed.

San Francisco saw only an inch of rain but Venado in Sonoma County got 5 inches (13 centimetres) over 24 hours.

Rain and winds forced the cancellation of more than 140 flights at San Francisco International Airport.

In Southern California, fog on a mountain highway triggered a 19-vehicle crash. Thirty-five people were evaluated for injuries after the pileup on Interstate 15 in Cajon Pass, but most declined to be taken to hospitals, the San Bernardino County Fire Department said.

In areas recently scarred by wildfires, authorities feared small rivers and creeks would flood their banks and cause massive mudslides, further damaging communities struggling to recover from a historically bad fire season.

The blazes stripped hillsides of trees and other vegetation that stabilize soil and prevent mudslides, putting at risk thousands of people living in foothill and canyon areas devastated by wildfires.

The hillsides were holding but people in burn areas were urged to remain alert.

In Malibu, a boulder crashed into a car, injuring the driver.