A 55-year-old man was killed when a tree fell, causing power lines to fall on his auto and electrocute him in in the Sherman Oaks district, in Los Angeles. An official at Los Angeles International Airport said 64 flights were cancelled and 269 delayed because of the storm.
Three people were killed as a powerful storms soaked Southern California, flooding freeways and knocking out power to tens of thousands.
Two people in a auto were rescued and four students on the bus were removed and taken to a school office, Mr Sherwin said. The storm stretched far out into the ocean and was at its strongest late on Friday afternoon.
It is part of a series of storms to have hit California recently, after the state suffered from five years of drought.
With 10 inches of rain expected in the mountains, 21 million people are under a flash flood watch.
Forecasters expect heavy rain throughout Monday for much of Northern California.
In Victorville, firefighters said one motorist died when their vehicle was submerged.
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Rain and wind wiped out play in golf's Genesis Open at the Riviera Country Club in Los Angeles, where a eucalyptus tree cracked.
The storm, which could be the worst to hit sourth California since 1995, is expected to last through Saturday, while further downpours are expected in the northern part of the state by the end of the week.
Crews are still cleaning the remnants of a mudslide on the 210 Freeway in Altadena, after heavy rains Friday night.
In downtown Los Angeles, 2.05 inches of rain fell as of 5:40 a.m. Saturday. The Los Angeles Department of Water and Power said electricity was knocked out for around around 82,000 customers as of 8 p.m., and Southern California Edison said 67,000 of its customers were without power as of 9 p.m.
Her leg was scratched by debris and "I was covered in sawdust", she said. That means there is a threat to life and property and people should take it very serious. This is actually in keeping with one of the early findings re: "west coast atmospheric rivers and climate change... that the numbers of atmospheric rivers will increase faster than their (average) intensities", he said.
Widespread urban roadway flooding is possible, along with flooding in creeks and small streams, and rock and mudslides, especially near canyon roadways. A record 1.96 inches fell at Long Beach Airport, breaking the daily rainfall record of 1.81 inches set in 1980.
Officials had hoped to lower the lake's level by 50 feet in advance of new rains, but fell significantly short of that goal, only reaching a 36-foot reduction by Thursday, according to local NBC News affiliate KCRA.
The storm's circulation will siphon the moisture in a south-to-north orientation, allowing it to butt up against the mountains in Los Angeles and San Diego counties, causing even heavier rains and heavy snow to fall in many spots.