One person was found dead on Friday in a rain-swollen flood-control channel in the Orange County town of Garden Grove, which could mark the third storm-related fatality on the West Coast since Thursday.
Separately, rescue teams saved two people after they were swept away in the fast-moving Los Angeles River near a homeless encampment, the Los Angeles Fire Department said in Twitter messages.
The Ventura County Fire Department said its personnel had responded to 37 flooding-related calls and that a second-story balcony collapsed in the Los Angeles suburb of Long Beach.
High winds tore down power lines throughout the region, leaving as many as 78,000 customers without electricity after the storm moved in before dawn, utility officials reported.
The National Weather Service warned that thunderstorms and even tornadoes were possible as the storm front advanced. A water spout was sighted over the ocean near Los Angeles International Airport on Friday morning.
The severe weather was