Photo

A home was consumed by the Valley fire early Sunday in Middletown, Calif.Credit Stephen Lam/Getty Images

LOS ANGELES — Two wildfires north of San Francisco forced thousands of people to flee their homes and prompted Gov. Jerry Brown to declare a state of emergency on Sunday, continuing a drought-fueled fire season that could be the worst the American West has ever endured.

The fires have burned through more than 100,000 acres, destroyed as many as 1,000 homes and commercial structures, and burned houses, schools and other infrastructure, according to the California Department of Forestry and Fire Protection, known as Cal Fire.

Hardest hit were the communities around Middletown, a town in Lake County just outside the Napa Valley. A fire that started on Saturday raced through the town overnight, reducing much of the area to ash as residents grabbed what possessions they could before escaping, witnesses said.

Maddie Ross, a student at Santa Rosa Junior College, fled with her grandparents and their three dogs from their home in Hidden Valley Lake after the flames leapt into their backyard.

“We were surrounded by fire,” Ms. Ross, 25, said. “It looked like hell everywhere. It was terrifying, truly terrifying. I’ve never been in a situation like that. We all felt like the world was coming to an end.”

The family grabbed the dogs and got into a truck in such a hurry that it left behind family photos that Ms. Ross had intended to pack and medication for her grandparents.

“The police just said, ‘Run!’” she said. “We didn’t even have shoes on.”

It took the three of them an hour to get out of the community because the roads were packed with hundreds of people trying to get out, Ms. Ross said. The family went west to Ukiah, where it was staying at a hotel full of Hidden Valley Lake residents who had left in trucks packed with supplies, pets and small livestock, she said.

The area is full of horse farms, and many of the animals were left behind.

Other owners took their horses with them to an American Red Cross shelter at the Napa Valley fairgrounds in Calistoga. About 300 people had taken refuge there on Sunday, and many of them were “thunderstruck,” said Gary Kraus, a former fire chief and now a Calistoga city councilman.

“There’s a sense of disbelief,” he said. “It will be an absolute miracle if we don’t start hearing about fatalities up there. You get heart attacks, accidents in cars, because this fire came through so quick.”

Dry conditions from the drought, high temperatures and gusty winds were contributing to “explosive” conditions, said Daniel Berlant, a spokesman for Cal Fire. The department has increased staffing and canceled scheduled time off, and it is accepting help from neighboring Nevada.

Firefighters have been moving farther afield to try to get ahead of the fire in Lake County, but each time the fire’s embers have jumped past them and they have had to move to a new area, evacuate more residents and try again to form a containment line, Mr. Berlant said.

“It doesn’t necessarily matter how many firefighters we put on it,” he said. “The fire just jumps right over us despite our valiant efforts.”

Southeast of Sacramento near the Sierra Nevada, more than 4,100 firefighters and personnel were battling the so-called Butte fire, which had burned more than 65,000 acres in Amador and Calaveras Counties and was only 20 percent contained on Sunday. Mr. Brown declared a state of emergency for those two counties on Friday.

The Butte fire had destroyed 81 homes and 51 buildings and threatened 6,400 more structures, according to Cal Fire.

Of the 13 fires that Cal Fire was responding to, the Butte and Valley fires posed the greatest threat to life and property, Mr. Berlant said.

The governor’s emergency orders free up state resources to help contain the fires and aid evacuees, and they mobilize the National Guard.

With the drought now the worst in California’s recorded history, the wildfire season this year has been devastating.

Since January, firefighters in California have responded to nearly 6,800 wildfires burning 545,000 acres, Mr. Berlant said. Cal Fire handled 5,000 of the wildfires, over 1,500 more than average, he said. The fires handled by Cal Fire this year have burned more than 150,000 acres, compared with 80,000 in an average year, he said. The figures do not include active fires.

Federal agencies were also battling a handful of fires that have engulfed more than 250,000 acres of national forests from the Oregon border to an area east of Fresno.

The total surface area of the active wildfires is more than 547 square miles. In comparison, the city of Los Angeles is 503 square miles.

The fire threatened to scorch the California wine industry at harvest time. Nearly half of the nation’s wineries are in California and concentrated in the Napa Valley and Sonoma County. Harvest season begins in late summer, and many wineries see an uptick in traffic.

Many of the workers who help keep Napa Valley’s famous wineries running live in the section of Lake County that was hit by the wildfire, said Michael Dunsford, the vice mayor of Calistoga, who owns a restaurant in town. The chef at his restaurant believed his house was gone, as did the manager of a restaurant down the street. With the road back to Middletown closed, neither of them had been able to go back to check on their homes.

“Lake County is the more affordable place to live,” Mr. Dunsford said, “so that’s where a lot of the employees for the wineries and the restaurants and hotels go. They’re the ones who are now being hit hardest and losing their homes.”