Some 680,000 homes and businesses were without power in the early hours of this morning, according to the poweroutage.us website, which tracks power connectivity nationally.

The worst affected counties were Mendocino, Yuba, Butte and Placer where 51,000 out of 146,000 customers were cut off.

The overall number of disconnections is falling however, from an overnight high of more than 780,000.

Firefighters rescued 16 people from Studio City, Los Angeles, late last night after debris carried by heavy rainfall caused significant damage to two homes.

All nine homes on Lockridge Road were evacuated, including pets, the Los Angeles Fire Department said in an update. "Thankfully, no one was injured and there are no medical needs," the statement said.

Emergency shelter is being offered to the displaced residents if needed. The homes are others in the area are now being assessed by the LA Department of Building and Safety, the Department of Water and gas suppliers.

Between 4 and 8 inches of rain have been forecast overnight.

A boat moored offshore is tossed by rough waters as the second and more powerful of two atmospheric river storms arrives to Santa Barbara, Calif., on Sunday.

San Bernardino County tonight declared a state of emergency due to "extreme" rain and snow expected through Wednesday.

The declaration clears the way for federal and state aid that will likely be needed during and after the storm, the county said in a press release.

"The National Weather Service has predicted catastrophic and life-threatening flooding for the San Bernardino valley and coastal slopes of the San Bernardino mountains tonight through Tuesday with showers chances lasting through Friday," the press release said. "Travel and commuting will be difficult."

Residents were also warned of small stream and urban flooding, as well as rising rivers.

The county "is taking all available steps to keep our residents safe and we are making preparations to meet their needs during and after the storms," county board chair and Third District Supervisor Dan Rowe said in the press release.

Cal State Los Angeles doesn't want students, faculty and staff members risking life and limb to get to its campuses tomorrow, so it's instructing them to stay put and learn online.

In a letter to the Cal State LA community, President Berenecea Johnson Eanes said that classes tomorrow will be held remotely and that faculty and staff members can work from home if their roles allow it.

Monday events at the main campus on the eastern edge of the city and at Cal State LA Downtown are canceled, and student services will be unavailable, she said.

The president said holding classes exclusively online was "the safest course of action."

An intersection in the San Fernando Valley region of Los Angeles flooded tonight, stranding several vehicles and those inside them to await rescue, a Los Angeles Fire Department spokesperson said.

The intersection of Oxnard Street and Donna Avenue in the Tarzana neighborhood was put under 2 to 3 feet of water amid heavy rain, the spokesperson, Nicholas Prange, said in an LAFD email alert.

LAFD swiftwater rescue teams were working to pull those people, who were not injured, out of those vehicles, he said. The motorists and any passengers did the right thing by staying put, he said.

"Thankfully the vehicle occupants have remained in their vehicles and not risked going out into the deep water with unpredictable terrain and currents below the surface," Prange said.

California State University, San Bernardino, said classes at its main campus, as well as those at its campus in Palm Desert, would be closed tomorrow.

"Faculty are encouraged to move instruction to virtual modalities and to communicate with students as soon as possible," the institution said in a notice to staff members and students. "Students should check with their faculty."

The two campuses will technically remain open, but for "essential operations only," the school said.

"Those staff who can telecommute are encouraged to do so," it said.

Nearly 1 million people in California were without power as the Pacific storm battered the Bay Area and set its sights on Southern California.

Most of the outages were in Santa Clara County, south of San Francisco, where 134,104 electricity customers were in the dark tonight, according to utility tracker PowerOutage.us.

The total number of homes, businesses and facilities without electricity went down from 913,283 to 893,420 as the night progressed, according to the tracker. However, a vast majority of Los Angeles County's 10 million residents were warned of imminent flash flooding, which could boost the number again.

A flash flood warning is in effect tonight for most of Los Angeles County's 10 million residents, including those in the cities of L.A., Long Beach, Pasadena and Pomona, according to the National Weather Service.

A warning means flooding is imminent or already underway. The warnings were also sent to cellphones of residents who allow wireless emergency alerts.

The warning urges residents to "move immediately to higher ground" and avoid walking or driving through floodwaters.