The storm brought heavy rains and cyclone-force winds, prompting the evacuation of more than a hundred homes threatened by mudslides near Los Angeles.
And in the LA area utilities companies said power was out for more than 100,000 customers.
The storm - the strongest to hit the Golden State in at least six years - was at its most fierce late on Friday afternoon, dropping over 8in (20cm) of rain in one area.
It was expected to last until Saturday afternoon.
The storm was a case of "bombogenesis", or "weather bomb", which occurs "when a mid-latitude cyclone rapidly intensifies, dropping at least 24 millibars over 24 hours", according to the National Oceanic and Atmospheric Administration (NOAA). A millibar measures atmospheric pressure.
The agency says a "weather bomb" can happen when a cold air mass collides with a warm air mass, such as air over warm ocean waters.
One man was found dead in a submerged car in the desert town of Victorville, about 100 miles (160km) east of Los Angeles, officials said.