SAN FRANCISCO » A windy storm sweeping down the West Coast knocked down trees, ripped through freeway and street signs, delayed hundreds of flights and knocked out power for thousands of people in California and Nevada.

Up to 10 inches of rain is expected this weekend in parts of the drought-stricken region, but the rainfall won’t make a significant dent in California’s historic drought.

Still, the storm is a welcome change after six dry weeks in the Bay Area. For the first time in recorded history, there was no measurable rainfall in downtown San Francisco in January, when winter rains usually come.

It would take 150 percent of the average rainfall for California to recover from the dry period, state water resource officials say. But snow is more important than rain because snowpack supplies about a third of the water needed by residents, agriculture and industry.

About 26 miles west of Seattle, an overflowing river inundated at least a half dozen homes on the Olympic Peninsula. Rescuers went door to door in Brinnon to check homes on a road partially blocked by a mudslide, Jefferson County Emergency Management spokeswoman Keppie Keplinger said.

Three people were rescued from a flooded pickup truck Friday morning, but none was injured, she said.

The threat of landslides will persist into the weekend, and weather officials warn of flooding in several rivers in western Washington. Oregon also saw flooding on roadways.

In the Sierra Nevada spanning California and Nevada, strong winds blinded drivers, causing multiple car crashes. The wind snapped massive trees, closed ski resorts around Lake Tahoe and knocked out power to thousands. A 134 mph gust recorded early Friday near the Mount Rose Ski Resort southeast of Reno led the facility and two others to close.

At least a dozen people were hurt in multiple crashes on Nevada highways. No deaths were reported, but nine people were hospitalized in a crash on a stretch of U.S. Highway 95A that involved at least eight vehicles. Three other people were hospitalized with minor injuries after five cars crashed on U.S. 395 north of Reno near the California line.

In the San Francisco Bay Area, power lines were snapped by falling trees and the wind ripped through freeway and street signs. More than 60,000 people lost power. By Friday evening, 9,000 customers remained without power, Pacific Gas & Electric said.

North of San Francisco, businesses in Marin, Napa, Solano, and Sonoma counties stacked sandbags to prepare for possible flash flooding from swollen waterways as rain started falling in the North Bay.

Winds of up to 15 mph were recorded east of the city Friday morning, and the blustery weather knocked down trees and caused power outages, the National Weather Service said.

San Francisco International Airport saw delays of up to 90 minutes and about 175 flights canceled Friday.

The storm is expected to drop rain through Sunday, and the National Weather Service issued a heavy-rain, high wind-gust and flash-flood warning for the region through Monday.

The heaviest downpours are forecast in the North Bay, where up to 7 inches of rain is expected to overwhelm waterways and roadway-drainage systems, leading to flash flooding.

Urban areas could see up to 4 inches of moisture, while Marin and Sonoma counties could see 10 inches through Sunday, weather service lead forecaster Roger Gass said.

Rain has been nearly nonexistent across much of California and Nevada since Dec. 20, halting hopes for the drought to improve. California’s second snow survey this winter found the Sierra Nevada snowpack is far below normal after a dry, unusually warm January. A greater snowpack translates to more water for California reservoirs to meet demand in summer and fall.

Water resources managers said heavy rain and cooler temperatures in the next three months would be required for the snowpack to build and give Californians hope for beginning to recover from the drought this year.

Associated Press writers Doug Esser in Seattle and Scott Sonner in Reno contributed to this report.