And forecasters warn more are on the way.
Images from the popular seaside town of Santa Cruz are just one example of the flooding to hit the state, along with torrential downpours, high winds, and even heavy snow in some areas.
SETH SHAPIRO, SANTA CRUZ RESIDENT: "As soon as I came out, it was just this huge wind gust, just swept over our area and trees blowing and a lot of rain just came in very quickly."
Storm surge spilled from the sea over roadways.
As of Thursday 180,000 homes and businesses were without electricity, according to the website Poweroutage.us, mostly in northern and central California.
The latest storm was powered by two overlapping phenomena: an atmospheric river, which is a stream of dense moisture from the ocean, and what's called a "bomb cyclone," which is a sprawling, hurricane-force low-pressure system.
Climate change has increased the frequency and intensity of such events, compounded by years of drought.
The National Weather Service says flash flooding and mudslides are also a threat in places saturated by repeat downpours, with the most vulnerable in areas where wildfires have scoured the earth of vegetation.
Similar back-to-back storms are coming in the next few days. At least six people have been killed in the severe weather since New Year's weekend.
