OJAI, Calif.  — California kept burning on Friday, raging wildfires cloaking Southern California in nightmarish flame and towering smoke visible from miles away.

As the fires spread for a fifth day, much of the region also faced a lingering threat posed by the dense smoke. Public health officials warned of dangerously bad air quality and said it was particularly threatening for the elderly, children and people with respiratory or heart conditions. Los Angeles County issued smoke advisories, urging people to remain indoors when possible, while Santa Barbara County officials said they expected to distribute 50,000 masks to residents.

Phil Moyal, an air quality specialist in Ventura County, said the smoke was causing hazardous conditions there, especially in the Ojai Valley, which is surrounded by mountains that have been trapping the smoke.

“When we say ‘off the charts,’ we mean off the charts,” Moyal said Friday about air quality measurements there. “I would not want to be there too long. . . . I would tell people to go to Seattle. There are not many places in Southern California that are clean or will stay clean, and that can change in a minute depending on the wind.”

President Trump on Friday declared an emergency in California, ordering federal aid to the state in response to a request from Gov. Jerry Brown, D. Firefighters, joined by reinforcements from outside the state, battled blazes that cropped up along a stretch of southwestern California.

Hundreds of buildings have been destroyed and thousands more remain at risk as more than a half-dozen blazes continued to burn, officials said. The largest fires Friday combined to burn across nearly 250 square miles.

The Thomas Fire in Ventura County – the biggest blaze in the state – continued to grow and threatened a host of cities in its path. Further south, authorities in San Diego County ordered thousands to leave as they fought the Lilac Fire, which injured three civilians and two firefighters.

The winds fanning the flames were lighter Friday, but forecasts call for them to increase again through Sunday. Red flag warnings of heightened fire risk will remain for at least Los Angeles and Ventura counties through Sunday, when winds could peak at around 50 mph. That could combine with extremely low humidity to create more erratic fire behavior and severe conditions for firefighters on the ground.

“We’re not out of the woods yet,” Dianne Jacob, chair of the San Diego County Board of Supervisors, said Friday at a news briefing. “We need to stay vigilant and be prepared.”

Across the region, people who fled recounted fire and smoke that seemed to come from everywhere. The sounds of helicopters woke Patricia Hampton and her boyfriend at their house in Ventura as the Thomas Fire was growing. When they looked outside, the ground was covered in ash, the air so smoky it was hard to breathe, she said. They hopped on bicycles and tried to flee.

“We didn’t know what had happened,” Hampton, 48, said at a temporary shelter at the Ventura County Fairgrounds on Thursday, two days after leaving home. “We rode down into town trying to make sense of what we were seeing – police everywhere, firetrucks, helicopters. It was like a war zone. You could hear transformers blowing up.”

In Los Angeles, Lili Hamedi said she went into her yard during the week and found her swimming pool filled with ash.

“We were surrounded by the fires,” said Hamedi, who lives in the Encino area. “I heard the fire. I never knew you could hear a fire.”

In Ojai, the favorable weather Friday allowed fire crews to make progress against what had been multiple lines of flames in recent days. A morning offshore wind calmed to nothing by midday, then shifted to a light breeze that had firefighters near Ojai preparing to defend the western edge of the city.

Along the Thomas Fire’s northern edge near Carpinteria, a small city in Santa Barbara County, fire crews, backed by helicopters dropping water near homes and ranches, made great strides against multiple blazes Friday morning and throughout the day. Parts of the city remained under mandatory evacuation orders, but the flames just miles away the previous day had turned into smoldering plumes of smoke.

This let fire crews concentrate on Ojai, a quirky town where New Age and the Old West mix in the hills high above Ventura. It has been surrounded by the Thomas Fire for much of the week.

Over several breezeless hours, smoke settled into the canyons and dry river beds, complicating visibility for the helicopters making drops to the north and west of the city. For firefighters, the stillness meant the wind was shifting, so they had to get ready, said Forrest Rowell, a battalion chief and strike team leader from the Sacramento Metropolitan Fire Department.

“We’re preparing to go in and keep the fire off the city from the north, and clean up some edges that could worsen with the new wind,” Rowell said.

The smoke spreading through Ventura pushed Jet Kauffman to pack up her two dogs, two cats and valuables into a car.

“Everything is literally burning around you and it’s raining ash and ember, and things are just lighting on fire around you, and you can’t really do much to stop it,” Kauffman said.

Her boyfriend, Shaun Kelleher, stayed behind to protect the Victorian house he bought in 2012. He looked out a back window and saw the glow creeping over the hillside, consuming palm trees in its path. The 32-year-old, ignoring mandatory evacuation orders, threw a scarf over his mouth and goggles over his glasses and ran outside to douse the home and yard with a hose.

“I saw a house light on fire, and that’s when I started to freak out, because there was no one around,” Kelleher said.

A second house burst into flames, then a third, and then an apartment complex. Fire and smoke were getting closer to his house and the wind was picking up. Kauffman, at a friend’s house, called Kelleher and pleaded with him to leave.

Then he heard a sound that filled him with relief: Sirens. Some 20 firetrucks pulled into the area, he said, and firefighters stopped the flames bearing down on the house.

The couple ended up in Thousand Oaks, a nearby city, staying with Kelleher’s father. Their Victorian home in Ventura had no power or drinkable water, but it was still standing.

Ventura resident Nate Weber wasn’t so fortunate. The anesthesiologist and his wife Christine fled Monday evening with their four- and two-year-old daughters to his mother’s house in Oxnard Shores.

Early the next morning they got a call from a neighbor: their home at the top of a hill on Mint Lane was gone. Nate returned to find sympathetic neighbors crowded around what remained of his house.

He said the experience was “similar to a friend dying.”

“I lived in that house six years, but it was a very formative six years,” he said. “I got married, I had two kids – just watching the kids grow up in that house, all those memories.”

The kids, too, have had trouble processing the loss.

When he showed his 4-year-old daughter a picture of the burned home, she remarked about how sad it was.

“Then she goes off to play,” he said. “Two hours later she said, ‘Dad, I’m ready to go home.’ “