Forestville, California - A massive storm system stretching from California into Nevada sent rivers climbing out of their banks, flooded vineyards and forced people to evacuate after warnings that hillsides parched by wildfires could give way to mudslides.
Northern California's Russian River rose to its highest level since 2006, and schools and roads were closed across the wine-making region of Sonoma County, where thousands of people were without power.
Avalanche concerns kept some California ski areas closed for a second day Monday in the Sierra Nevada. Forecasters said more snow and rain was on the way.
In Nevada near Reno, Nevada National Guard high-water vehicles were deployed to help people evacuate from a town.
The Russian River is prone to flooding, but this year's flood has been particularly worrisome because it threatened to topple trees weakened by six years of drought.
Jeff Watts, an artist, spent an anxious night listening for the sound of falling trees on his land. On Monday, he found his drive to work blocked by a tree that had fallen on a car. Emergency crews were working to extract the vehicle.
"I couldn't get past the tree, so I turned around and I'm doing this," said Watts, who had pulled over to photograph oak trees and their reflections in the floodwater.
Over the weekend, toppled trees crashed against cars and homes and blocked roads in the San Francisco Bay Area. Stranded motorists had to be rescued from cars stuck on flooded roads.
A giant tree fell across a highway in Hillsborough to the south of San Francisco, injuring a driver who couldn't brake in time and drove into the tree. And a woman was killed Saturday by a falling tree while she took a walk on a golf course.
To the south near Los Angeles, commuters were warned of possible highway flooding and mudslides in hilly areas.
Emergency workers in Nevada voluntarily evacuated about 1,300 people from 400 homes in a Reno neighborhood as the Truckee River overflowed and drainage ditches backed up.
In the city of Sparks neighboring Reno, Bob Elsen said he never expected so much rain in Nevada's high desert, where only 8 inches of precipitation normally falls each year. He moved to Sparks from perpetually wet Bremerton, Washington.
"I don't think I've seen this much rain since I moved here six years ago," Elsen said, watching the Truckee River rise. "It's why I moved out of Washington to get away from this stuff."
The worst flooding in Sparks was expected to send several feet of water early Monday into an industrial area where 25,000 people work.
The back-to-back storms that have hit California and Nevada since last week are part of a so-called "atmospheric river" weather system that draws precipitation from the Pacific Ocean as far west as Hawaii with potentially catastrophic consequences for areas hit by the heaviest rain.
Schools were also canceled in Reno and Sparks, and Gov. Brian Sandoval told all nonessential state government workers to stay home Monday after he declared a state of emergency.
In California's Calaveras Big Trees State park, a well-known giant sequoia tree known for the huge tunnel carved through its trunk that cars once passed through came toppling down, The San Francisco Chronicle reported.
Park volunteer Joan Allday said the tree had been weakening and leaning severely to one side for several years. "It was barely alive. There was one branch alive at the top," she told the newspaper.
Farther north, two major highways across the Sierra Nevada were partially closed because of mudslides and roads leading to Yosemite National Park's valley floor remained were closed amid fears that the Merced River could overflow and cause major flooding.