LOS ANGELES — With thick plumes of smoke, towering flames and mass evacuations, a fast-moving wildfire struck one of America’s major cities on Wednesday.

As fires raged out of control across Southern California, a new blaze erupted in the Bel-Air neighborhood of Los Angeles, near iconic landmarks like the UCLA campus and the Getty Museum, home to old masters paintings and ancient Roman statues.

It burned up to the edges of the 405 freeway, the nation’s busiest highway carrying about 400,000 vehicles a day, where the northbound lanes were closed for much of the day and commuters drove through a shower of ash with flames rising in the horizon.

Forty miles to the northeast, the largest of several fires underway had consumed by Wednesday 65,000 acres and at least 150 structures — probably many more, fire officials said — and threatened 12,000 others in the city of Ventura and neighboring communities, and was zero percent contained. Other major fires were burning in the northern San Fernando Valley and the rugged region north of Los Angeles.

The fires compounded the suffering of what has already been one of the state’s worst fire seasons on record, including the blazes that ravaged the wine country north of San Francisco in October. The new outbreaks have forced nearly 200,000 people in the Los Angeles and Ventura areas to evacuate, officials said, and extremely high winds are likely to make matters worse on Wednesday night and Thursday.

Fire season usually peaks in October in California, but officials suggested that with climate change, more fires are occurring later in the year.

“These are days that break your heart,” Mayor Eric Garcetti of Los Angeles said at a news conference. “These are also days that show the resilience of our city.”

It was a day in which smoke from the fires ringing the region could be spotted from the Santa Monica Pier, the streets of downtown and the beaches of Santa Catalina Island. And in a city where residents live outdoors, many stayed home to avoid the foul air.

The fire in Bel-Air consumed just 150 acres and a handful of structures, small figures compared with some of the other blazes. But in such a densely populated area, the prospect of warm, dry Santa Ana winds whipping the flames into other neighborhoods had many residents of Los Angeles’ west side preparing for possible evacuation. Officials ordered 700 homes in Bel-Air evacuated.

A gray-brown pall, tinted orange in places, hung across a region that is home to millions of people, and the regional air quality agency warned that the air posed a health hazard in places.

At least four houses burned in hilly Bel-Air, where sprawling villas costing tens of millions of dollars are home to celebrities and other wealthy Angelenos.

Winds could still reach 80 mph, said Chief Ken Pimlott of Cal Fire, the state firefighting agency. “These will be winds where there will be no ability to fight fires,” he said. Wind blowing from the northeast raised fears that the fire could jump the freeway, into the area around the Brentwood neighborhood and where the sprawling Getty sits on a hilltop overlooking the 405.

The fires in total destroyed more than 300 homes, businesses and other buildings.

Fire and smoke forced the closing of the 101 freeway — the main coastal route north from Los Angeles. More than 1,700 firefighters were working on the blaze there.

Hundreds of schools were ordered closed for the rest of the week because of the thick blanket of smoke filling the skies. At the University of California at Los Angeles, officials said an electrical failure in the area left the campus without power. The student health centre was distributing masks to students to help protect them from the smoke wafting over the campus.

Garcetti declared a local state of emergency because of the Skirball Fire, as the blaze in Bel-Air is called. Gov. Jerry Brown issued a similar call for the Ventura fire on Tuesday. The declarations asked for rapid aid from state and federal officials.

Jennifer Medina/Richard Pérez Peña/The New York Times