A series of storms drenching California could be the largest weather system the region has seen in a decade, the U.S. National Weather Service says.
Forecasters have warned of possible flooding and mudslides in the same area decimated last year by what became known as the Station wildfire, north of Los Angeles.
Warnings have been issued for Los Angeles, Ventura and Santa Barbara counties.
Northern California was expecting 12 centimetres of rain in places over the weekend, and officials in San Francisco were distributing sandbags to residents.
Southern California could see five to 10 centimetres along the coasts and valleys, with triple that amount in the mountains.
The Central Valley will likely get two to seven centimetres of rain by Monday with up to 38 centimetres of rain in the Sierra Nevada mountains, which could prompt flooding in streams and rivers, National Weather Service meteorologist Jim Dudley said Friday.