LOS ANGELES (Reuters) - Heavy rains and flooding along rivers forced the evacuation of thousands of people in a California wine making region and an area of Nevada east of Lake Tahoe on Monday, officials said, with more storms on the way.

Regions of California and Nevada, two states which have suffered from drought for years, were walloped by storms over the past week from a weather system called the “Pineapple Express” that sent moisture streaming from Hawaii.

The storms have knocked out power for more than 570,000 customers of Pacific Gas and Electric in northern and central California since Saturday, but electricity has been restored to almost all of them, said company spokesman Tom Schmitz.

The storms are the latest in a wet winter expected to put a considerable dent in California’s years-long drought.

Just north of San Francisco, rains caused the Russian River in Sonoma County to flood early on Monday, the county Sheriff’s department said.

That led to the evacuation overnight of more than 3,000 residents in the area of Guerneville, Jonathan Gudel, a spokesman for the California Governor’s Office of Emergency Services, said by phone.

In Nevada, residents of about 400 homes in Reno were ordered to evacuate on Monday as rains swelled the Truckee River, which flows through the city, Washoe County health agency spokesman Phil Ulibarri said by phone.

Slideshow ( 14 images )

Officials in both California and Nevada said they were still assessing flood damage on Monday.

Over the past week, the storms brought 10 to 15 inches (25 to 38 cm) of rain and snow to the Sierra Nevada mountains in California and lesser amounts of precipitation in western Nevada, meteorologist Bob Oravec of the Weather Prediction Center said by phone.

A woman died after she was struck by a falling tree on Saturday in the San Francisco Bay area, with a local fire official saying the weather appears to have caused the tree to topple, according to Bay Area News Group.

Over the weekend, wineries in California’s Napa Valley were spared damage from the heavy rain, which is expected to replenish water supplies for the state’s wine-making industry after five years of drought, said Patsy McGaughy, a spokeswoman for the Napa Valley Vintners.

“We’re actually grateful to see the rain,” McGaughy said.

In a sign of the rain’s intensity, California officials for the first time in a decade were considering opening floodgates at a weir on the Sacramento River to prevent flooding in areas of Sacramento, Lauren Hersh, a spokeswoman with the state Department of Water Resources, said by phone.

Slideshow ( 14 images )

On Sunday, 27 homes were damaged from flooding in Monterey County south of San Francisco when the Carmel River breached its banks, swamping some nearby properties, and rainwater inundated homes in the town of Seaside, Gerry Malais, the county emergency services director, said by phone.

Also this weekend, an ancient giant sequoia tree with a hollowed-out tunnel big enough for cars to drive through was toppled by floods in Calaveras Big Trees State Park just southeast of Sacramento.

The storms weakened early on Monday but were expected to return in full force later in the day and last until Wednesday, Oravec said.

California officials have not yet declared an end to the drought since water still remains relatively scarce in the southern part of the state.

But northern California’s Lake Oroville, the principal reservoir for the State Water Project, has 2.25 million acre feet of water, while a year ago it held about 1 million acre feet, Michael Anderson, state climatologist for the California Department of Water Resources, said by phone.