LOS ANGELES — Four wildfires roared through Southern California on Tuesday, forcing the evacuation of tens of thousands of people and destroying hundreds of homes and other buildings in the latest chapter of what has been one of the state’s worst fire seasons.
The first fire, in Ventura County, started Monday evening and was still “out of control” on Tuesday night, the authorities said. Named the Thomas Fire, it began north of Santa Paula, California, and spread rapidly overnight on Monday to envelop at least 50,000 acres, destroying hundreds of structures and prompting 27,000 people to evacuate, including some from the city of Ventura.
Three more fires began on Tuesday. One in Los Angeles County quickly grew to encompass more than 11,000 acres and destroyed more than 30 structures. Another, in San Bernardino County, injured three people as it burned 100 acres of vegetation. And a fourth, near Santa Clarita, tore through at least 5,000 acres, forcing the evacuation of a trailer park and several schools.
The exact causes of the fires were not immediately known.
“You look at your window and see flames, you know you have to go,” said Anne Forsyth, an administrator at Thomas Aquinas College, a small Catholic college less than 3 miles from where the Ventura County fire began. It evacuated on Monday.
“The speed with which this spread, I’ve never seen that before,” Forsyth said. “I don’t think anyone here had seen that before.”
The authorities said the fires were fed by dry conditions and fierce winds. Gov. Jerry Brown declared a state of emergency for Ventura County, where he said the flames had destroyed hundreds of homes.
“This fire is very dangerous and spreading rapidly, but we’ll continue to attack it with all we’ve got,” the governor said in a statement. “It’s critical residents stay ready and evacuate immediately if told to do so.”
The Thomas Fire spread with astonishing speed. The sheriff’s office received its first reports at 6:24 p.m. Pacific time on Monday. By midnight, the fire was estimated to have reached 10,000 acres.
“Realistically, people have no idea what’s going on or how bad this is,” said Kat Jones, 38, who evacuated her home in the Ojai Valley, far from where the blaze began, in the early hours of Tuesday morning. “The fire has moved so fast, it is so big and it really hard to predict, I think it is overwhelming to everyone.”
The mayor of Los Angeles, Eric Garcetti, said the weather stoking the fire in Los Angeles County would probably continue for the next five days. The dry conditions and high winds forecast through at least Thursday are expected to significantly expand the affected area.
“It’s a very difficult moment, but we will get through this,” he said. “We are a resilient city, we are a strong city, we are a capable city.”
California has seen some of its most destructive fires ever this year. In October, even as more than a dozen fires broke out in the northern part of the state, a separate one quickly grew in the Anaheim Hills, burning through thousands of acres. The fires have collectively killed more than 40 people and destroyed thousands of homes and businesses.
A month earlier, the La Tuna Fire sent smoke billowing into the air above Los Angeles as the hills glowed red.
Sgt. Eric Buschow of the Ventura County Sheriff’s Office said that the Thomas Fire, which was fueled by the Santa Ana winds, was one of the worst he had seen, partly because of the number of homes that were affected. Frequently, he said, those strong winds push fires toward the ocean, burning through less inhabited canyons and their dense brush along the way. Fires like those do not typically affect as many neighborhoods as the Thomas Fire did, he said.
At least 186,000 people were without power in Ventura County on Tuesday, many of them in the affected area. The power failures made it difficult for the 1,100 firefighters working there to battle the flames.
In Los Angeles County, about 700 firefighters and 200 police officers were responding to the fire, named the Creek Fire, officials said.
Garcetti warned that the smoke was causing a severe degradation in air quality, one that was significantly worse than a Stage 3 smog alert. He cautioned those who had asthma or were otherwise sensitive to air conditions to stay indoors.
Daryl L. Osby, the county’s fire chief, said that the Creek Fire had been reported overnight, as his department was busy fighting the fire in Ventura. He said it was extreme and erratic “in ways that people may not have experienced in the past,” adding that five years of a continuing drought and unpredictable winds, with gusts up to 70 mph, were partly to blame.
“We are in an extreme firefight right now, trying to protect lives and save property,” he said.