Evacuations were ordered in the middle of the night in San Bernardino.

Multiple homes were consumed by flames in the San Bernardino area after a brush fire ignited early on Thursday and quickly grew to engulf 200 acres, the latest eruption of wildfire in California.

Firefighters got the call about a brush fire near Highway 18 shortly after 1 a.m. and arrived to find several homes threatened by the fire, which has been named the Hillside fire. So far, six homes have been damaged or destroyed.

“When we first got on scene of the fire, we had a wind-driven, rapid-rate-of-spread fire heading downhill into the City of San Bernardino,” said Scott Howes, deputy fire chief for the San Bernardino National Forest. He said more than 500 firefighters were battling the blaze.

The fire is being driven by Santa Ana winds gusting up to 40 miles an hour, as several other fires in Southern California have been this week. With multiple fires raging up and down the state, local fire departments have often had to wait for the chance to use aircraft and other firefighting tools that are deployed assisting other agencies.

“We’re competing for resources right now with several other fires,” Kathleen Opliger, a deputy chief of the San Bernardino County Fire Department, said at a news conference.

Homeowners in the area saw orange flames lighting up the hills around the northern edges of the city in the early morning hours, and then cascading down to threaten neighborhoods to the west of Highway 18. About 1,300 residents in 500 homes have been evacuated.

The highway, which connects the city of San Bernardino with the mountains to the north, was closed because of the fire, according the California Highway Patrol.

“It’s very fast-moving,” Chris Prater, a spokesman for the San Bernardino County Fire Department, said of the fire. “We do have very strong winds coming out of the north-northeast, facilitating the fire spread.”

An earlier blaze, the Old Water fire, swept through the area last week. This week, dry conditions and low humidity were making the Hillside fire difficult to fight, Mr. Prater said. “We’ve had these winds for the past few weeks, and it’s dried out the fields.”

In Jurupa Valley, strong winds are feeding the flames.

Another fire grew to cover 300 acres in Jurupa Valley, southwest of San Bernardino, on Thursday morning, damaging at least three structures and prompting evacuation orders for about 2,000 homes, said Jeff LaRusso, a spokesman for the Riverside County Fire Department.

“We’re still under Santa Ana wind conditions, so with the winds blowing and the extremely low humidity, the fire will probably grow throughout the day,” he said, pausing as a helicopter passed overhead.

“We’re hitting it with both rotary and fixed-wing wing aircraft, and about 300 firefighters are on scene right now,” Mr. LaRusso added.

Lissa Washburn, 43, a San Bernardino resident, said smoke was polluting the air even at her home, which not in the evacuation zone for either the Hillside fire or the one in Jurupa Valley, named the 46 fire. “It smells like fire outside, and our cars are covered with ash,” Ms. Washburn said.

Firefighters battling the Kincade fire are optimistic.

Firefighters in Northern California believe they have “turned the corner” in battling the Kincade fire, which was 60 percent contained by Thursday morning.

At a Wednesday night news conference, the authorities listed several positive signs: Air quality was improving. Strong, gusty winds had subsided. And most of the roughly 190,000 residents who were evacuated had been cleared to return to their homes.

“We believe that most of the threat is now in our rearview mirror, and we are moving forward here,” said Mark Essick, the Sonoma County sheriff.

The fire had burned 76,825 acres, destroyed 266 structures and damaged 47 others as of Thursday morning. More than 5,200 firefighting personnel were still on the scene, some of whom worked through the night. The authorities cautioned that despite the good news, the fire could still behave unpredictably, as humidity remained low and there was no rain in the forecast.

But Jonathan Cox, a division chief with Cal Fire, the state’s firefighting agency, said firefighters were also shifting their focus away from the front lines and toward “secondary hazards,” including pockets of embers and trees in danger of falling.

In Southern California, a different picture emerged. A fast-moving brush fire that began early Wednesday — and burned its way 100 yards from the Ronald Reagan Presidential Library and Museum — was still raging.

As of Wednesday night, that fire, known as the Easy fire, was 5 percent contained and had burned nearly 1,500 acres, threatening 7,000 structures.

A new state web portal includes links to updates on fire status, evacuation zones, power outages, shelters and housing, road conditions and other information related to the fires, compiled by state agencies like Cal Fire and Caltrans and by utility companies.

Goats may have helped save the Reagan Presidential Library.

When the flames of the Easy fire were racing toward the Ronald Reagan Presidential Library and Museum on Wednesday, coming as close as 100 yards away, they were apparently slowed not just by the efforts of fire crews but also by an unusual but time-tested fire-prevention measure.

Every year in May, the Ventura County Fire Department deploys about 500 goats to munch through the grass around the library and clear away dry vegetation that can fuel a spreading fire.

The method may sound odd, but hungry goats have been used for decades to clear brush, from California to Florida to Portugal.

“They used to send out firefighters who did it all by hand, but now it’s done by goats,” said Melissa Giller, a spokeswoman for the library and museum.

The complex has many features to keep its precious memorabilia safe if a fire does enter the grounds, including powerful sprinklers and fire doors, Ms. Giller said. And for good reason: The museum houses a plane that served as Air Force One for seven presidents; a piece of the Berlin Wall; and many of the papers from Mr. Reagan’s eight years as president and eight years as governor of California.

Some Sonoma County residents returned home.

On Wednesday, officials at Cal Fire lifted some mandatory evacuation orders around the Kincade fire, allowing thousands of people to return to their homes.

Two of those places were the communities of Windsor and Healdsburg, with a combined population of about 40,000 people, where evacuation orders were downgraded from mandatory to voluntary.

Maricela Garcia, 29, was among those who rushed back home. She is 35 weeks pregnant and had fled on Saturday with her 5-year-old son, her husband, a few changes of clothes and a pillow.

She is ready for things to get back to normal, she said outside her house on a tree-lined block. “I’m just glad we have a home to come back to,” she said. They still have no power, and the refrigerator is full of food gone bad. But she said she could not be mad at officials for evacuating them. “They were just trying to keep everybody safe.”

Elsewhere in Windsor late Wednesday, the traffic lights were still out, but people were beginning to stream back in, their pickup trucks and sedans loaded with suitcases and pets. On one corner, a cluster of people stood on the road with a large banner that read “Welcome home Windsor residents.” They jumped up and down and flashed thumbs-up signs as their neighbors honked their horns.

Maps show where the fires are burning now.

We’re continuing to update our page of maps showing the extent of the fires, power outages and evacuation zones.

Santa Ana winds drive flames and imperil crews.

The winds known as the Santa Anas — the defining antagonist of the fire season — loom large over the collective psyche of Southern California, where many residents call them devil winds. Forecasters said they would be blowing hard again on Thursday, after whipping up to near-hurricane strength on Wednesday and making the Easy fire in Ventura County uncontainable.

Once the winds reach a certain strength, there is little that fire crews can do to halt a fire, said Brian McGrath, a spokesman for the Ventura County Fire Department. “We can’t get in front of it, because it puts us in harm’s way,” he said.

On the hillsides near the Ronald Reagan Presidential Library and Museum in Simi Valley, threatened by the Easy fire, the winds made it a challenge even to walk — slowly, hunched over, both hands holding your hat. Flags snapped, tree branches bent and cracked, and a portable sign toppled over.

Though the Santa Anas blow nearly every year, they have been especially strong lately, and many residents said they felt different. With the effects of climate change combined with a fierce fire season, the winds now seem more ominous.

Robert Santos, a meteorologist for Spectrum News 1, a local cable channel, said big temperature drops in the mountains and high desert country inland produce masses of cold, heavy air that push out like the opening of a freezer, producing strong gusts of dry wind downhill toward the ocean.

Strong seasonal winds have also created problems in Northern California, fanning the flames of the Kincade fire and others and prompting utility companies to shut off electric power over wide areas in the hope of avoiding new blazes started by wind-damaged lines and equipment.

The National Weather Service has posted rare “extreme red flag warnings” for much of Los Angeles and Ventura Counties through 6 p.m. Thursday, saying the winds could cause “extreme fire behavior.”

Wind conditions in Northern California, where red-flag warnings expired in most areas on Wednesday evening, were expected to be much less severe on Thursday. But the weather threatened to throw firefighters battling the Kincade fire another curve overnight: temperatures well below freezing.

Utility equipment is suspected in the Easy fire and others.

California regulators said on Wednesday that they were investigating whether Southern California Edison’s equipment had played a role in the Easy fire in Ventura County, after the utility said it found “circuit activity” close to the time the fire was reported.

The disclosure was one of several on Wednesday in which officials said they were eyeing the hardware of California utilities in connection with fires, including at least four that ignited in the Bay Area on Sunday.

Pacific Gas and Electric, California’s largest utility, shut off power to nearly 1 million customers this week in the hope of keeping its equipment from sparking new fires. It was the largest public safety blackout in California history.

By late on Wednesday, PG&E said it had restored power to about 95 percent of those customers, leaving about 53,000 business and residential customers still in the dark, a figure that translates to roughly 130,000 people affected. Power was completely restored in 23 of the 37 counties that were affected by the shut-offs, the company said.

Despite the company’s precautions, a vegetation fire broke out under its power lines in Bethel Island, Calif., on Sunday and grew to the size of a football field, threatening a new housing development, before being brought under control, the East Contra Costa Fire Protection District said. The district said another fire that prompted some evacuations in Oakley, Calif., started after PG&E equipment cast sparks 200 yards away.

PG&E told California regulators it was also investigating whether a transformer and an open wire were responsible for two fires in Lafayette, Calif., on Sunday.

Reporting was contributed by Julie Turkewitz in Windsor, Calif., Tim Arango in Simi Valley, Calif., and Mihir Zaveri, Jacey Fortin and Nicholas Bogel-Burroughs in New York.