A powerful Pacific storm blew into Southern and Central California with wind-driven heavy rains that downed power lines and electrocuted a man, stranded others in flooded areas and disrupted hundreds of flights at airports.

With the storm feeding on an atmospheric river of moisture stretching far out into the Pacific, precautionary evacuations of homes in some neighbourhoods were requested on Friday due to the potential for mudslides and debris flows.

More than 300 arriving and departing flights were delayed or cancelled at Los Angeles International Airport.

In the Sherman Oaks area of Los Angeles, a falling tree downed power lines and hit a car. A 55-year-old man was electrocuted and pronounced dead at a hospital, police and fire officials said.

Winds gusting to 60 mph or more lashed the area. Heavy rains turned creeks and rivers into brown torrents and released slews of mud from hillsides burned barren by wildfires. Several stretches of freeways and highways were closed by flooding.

"It's crazy," said Robin Johnson, an academic adviser at the University of California, Santa Barbara. "It's just pouring down rain. The wind is just going nuts." 

"At one point the wind was so strong I'm surprised it didn't blow my windows out," retiree Phoenix Hocking said in a Facebook message from Carpinteria. "I now have a pond in my patio. And my dog is starting to grow flippers so he can go out and do his business." 

In San Bernardino County, a 20-mile stretch of State Route 138 in the West Cajon Valley was closed at the scene of a summer wildfire.

Mud sloshed over concrete rail barriers and about two dozen vehicles, including big-rigs and a school bus, were either mired in mud or became unable to turn around on the closed road and some were abandoned, county fire spokesman Eric Sherwin said.

In LA's Sun Valley, 10 cars were trapped in swift-moving water on a roadway and eight people had to be rescued, the Fire Department reported.

Two people in a car were rescued and four students on the bus were removed and taken to a school office, he said.

Another road in the area was covered with 2 feet of mud.

Using ropes and inflatable boats, firefighters rescued seven people and two dogs from the Sepulveda basin, a recreation and flood-control area along the Los Angeles River. One person was taken to a hospital with a non-life threatening injury.

The storm took aim at Southern California but also spread precipitation north into the San Joaquin Valley and up to San Francisco. It was not expected to bring significant rain in the far north where damage to spillways of the Lake Oroville dam forced evacuation of 188,000 people last weekend.

The National Weather Service said it could end up being the strongest storm to hit Southern California since January 1995.