The storm passed northward through Mexico's Baja California peninsula, where Pacific hurricanes are expected.

Rescue teams, including divers, were working in the region, the county says, although no deaths or injuries have been reported.

Up to 23cm of rain were expected in some parts of the state, with several feet of heavy, wet snow falling over mountains where a huge snowpack has built up over months of near-record storms.

The latest spasm of gun carnage struck the coastal town of Half Moon Bay, where a gunman opened fire on groups of farm workers at two locations, leaving a total of seven dead and one badly wounded.

Huu Can Tran, 72, used a semi-automatic pistol in a rampage in the Los Angeles suburb of Monterey Park on Saturday night, killing men and women in their 50s, 60s and 70s.

The Monterey Park shooting is the country's deadliest since a gunman in Uvalde, Texas killed 22 people at an elementary school last May.

Investigators believe a gang or drug cartel targeted the family, police say.

More than 11,000 homes remained without power Sunday in California.

Evacuation orders and warnings are widespread, with forecasters saying major roads could become impassable.

Authorities have issued ominous warnings of threats to life and property for a vast stretch of California, focused around San Francisco and Sacramento.

Detectives in the California city, where residents complain of a spike in crime, were granted permission this week to deploy machines capable of lethal force.

More than two decades of drought and rising temperatures, exacerbated by climate change, have made California more vulnerable than ever to wildfires.