LAKEPORT - A Northern California wildfire ranked as the most destructive to hit the drought-stricken US West this year has killed a woman and burned some 400 homes to the ground, fire officials said on Monday, and they expect the property toll to climb.

The so-called Valley Fire erupted on Saturday and spread quickly to a cluster of small communities in the hills and valleys north of Napa County's wine-producing region, forcing the evacuation of thousands of residents.

An elderly, disabled woman who was unable to flee her home died in the fire as flames consumed the building on Saturday evening, Lake County Sheriff's spokesman Lieutenant Steve Brooks said.

Evacuated residents recounted chaotic ordeals of having to flee their homes through gauntlets of flame, and some 9,000 structures remained threatened as darkness fell on Monday evening, according to the California Department of Forestry and Fire Protection (Cal Fire).

"That whole place was ablaze. It was like Armageddon," said Steve Johnson, a 37-year-old construction worker from Southern California who was visiting his mother in the fire-ravaged community of Hidden Valley Lake. "We were literally driving through the flames."

Johnson and his mother safely escaped and spent Sunday night at a high school gymnasium converted into an evacuation center.

By Monday evening, the blaze had blackened 62,000 acres (24,690 hectares) of tinder-dry forests, brush and grasslands, and was only about 10 percent contained, according to Cal Fire.

About 40,000 acres (16,190 hectares) of the landscape were consumed in the first 12 hours of the fire at the peak of its intensity on Saturday and early Sunday, stoked by high winds.

Fire officials described the rapid initial rate of spread as nearly unprecedented, a consequence of vegetation desiccated by four years of drought and weeks of extreme summer heat.

Four firefighters were hospitalized with second-degree burns in the early hours of the blaze on Saturday.

By Monday night more than 1,400 firefighters were battling the flames, one of 12 major wildfires across the state during an intense fire season.

The communities of Cobb, Middletown, Hidden Valley Lake and the Harbin Hot Springs resort - located about 50 miles (80 km) west of Sacramento, the state capital - were reported to be hardest hit by the fire.

Reuters video footage from Middletown, a village of about 1,500 residents, showed a smoking, devastated scene of burned-out vehicles, twisted, blackened debris and charred foundations of buildings that had been reduced to ash. Roughly half of the town was leveled.

The carcass of a horse was seen lying on the shoulder of the road between Cobb and Middletown, a stretch of highway where miles of houses were laid to waste on both sides.

"We were trying to get out. We were trying to hook up our trailer and all of a sudden, two houses up I see this big wall of pink and red and gray," said Carol Ulrich of Middletown. "So we just dropped everything and left. I didn't even get my purse, nothing. We just drove away and left our trailer and everything."

Janet Mondragon of Middletown, appeared close to tears as she watched videotaped footage of her home in flames.

"We have nothing, absolutely nothing," she said. "What can I tell you? We are staying in a hotel in Santa Rosa, but we're going to have to start life over. There is nothing, absolutely nothing."

Cal Fire on Monday reported that some 1,000 structures had been lost, at least 400 of them homes. Mark Ghilarducci, Director of the state's Office of Emergency Services, told reporters on Monday some 13,000 people had been displaced.

Governor Jerry Brown, who also spoke at the news conference, said climate change would continue to worsen fire conditions.

That tally ranks as the greatest loss of property from a single blaze in California this season, or among the scores of wildfires that have ravaged the drought-stricken western United States so far this summer, according to the National Interagency Fire Center in Boise.

The property toll is expected to rise as damage-assessment teams reach areas of the fire zone that have yet to be surveyed, but no additional communities were under immediate threat on Monday, Smith said.

The Valley Fire also damaged the cooling towers at five of the 14 steam-generating plants operated by Texas-based Calpine Corp at a sprawling geothermal field straddling the Sonoma-Lake county border, company spokesman Brett Kerr said.

A separate blaze raging since Wednesday in the western Sierras has destroyed 135 homes and 79 outbuildings and was threatening about 6,400 structures, with some 10,000 people displaced there too, officials said.

In Oregon, meanwhile, Governor Kate Brown invoked the state's so-called Emergency Conflagration Act on Monday, mobilizing additional resources as a fast-growing wildfire threatened 275 homes in a rural area of the state.