A powerful storm barreled toward Southern California after flooding highways, toppling trees and causing mud flows in areas burned bare by recent fires across the northern part of the state.

Drenching showers and strong winds accompanied the weekend’s arrival of an atmospheric river — a long and wide plume of moisture pulled in from the Pacific Ocean. The National Weather Service’s Sacramento office warned of “potentially historic rain.”

Flooding was reported across the San Francisco Bay Area, closing streets in Berkeley, inundating Oakland’s Bay Bridge toll plaza and overflowing rivers in Napa and Sonoma counties. Power poles were downed and tens of thousands of people in the North Bay were without electricity.

Also Read | Aftermath of California wildfires causes thousands of trees to be uprooted

By Sunday morning, Mount Tamalpais just north of San Francisco had recorded a half foot (15 centimeters) of rainfall during the previous 12 hours, the weather service said.

“Some of our higher elevation locations could see 6, 7, 8 inches of rain before we’re all said and done,” weather service meteorologist Sean Miller said.

About 150 miles (241 kilometers) to the north, the California Highway Patrol closed a stretch of State Route 70 in Butte and Plumas counties because of multiple landslides within the massive Dixie Fire burn scar.

“We have already had several collisions this morning for vehicles hydroplaning, numerous trees falling, and several roadways that are experiencing flooding,” the highway patrol’s office in Oroville tweeted on Sunday. “If you can stay home and off the roads today, please do. If you are out on the roads, please use extreme caution.”

Also Read | California proposes vicinity curbs between new drilling and community sites

The same storm system also slammed Oregon and Washington state, causing power outages affecting tens of thousands of people. Two people were killed when a tree fell on a vehicle in the greater Seattle area. Eastside Fire & Rescue responded to the scene of the fatalities near Preston, Washington, which is about 20 miles (32 kilometers) east of Seattle.

In California’s Colusa and Yolo counties, state highways 16 and 20 were shut for several miles due to mudslides, the state Department of Transportation said.