VACAVILLE — Firefighters hard-pressed by some of the largest wildfires in California history scrambled Wednesday to take advantage of cooler weather and an influx of aid as they carved and burned containment lines around the flames to prevent more land from burning.

“Every percent of containment is hours and hours of sweat and blood up on those lines,” Jonathan Cox, a deputy chief with California Department of Forestry and Fire Protection, said Tuesday evening.

Progress was made on three major blazes around the San Francisco Bay Area and authorities were making plans to allow people who evacuated fire-impacted communities to return to their homes.

Many Fires Sparked by Lightning

The fires, which started as clusters of lightning-sparked blazes last week, slowed down at lower altitudes as a morning marine layer — an air mass drawn from the ocean by intense heat on land — brought cooler temperatures and higher humidity. The cooler air, however, didn’t reach the higher forest and rural areas full of heavy timber and brush.

“The return of the marine layer has been a welcomed one,” the National Weather Service said early Wednesday.

Amid the good news there were sobering developments.

A fire in San Mateo and Santa Cruz counties south of San Francisco was 19% contained but damage assessments raised the number of buildings destroyed to more than 530.

Santa Cruz County officials reported that a woman who hadn’t been heard from since Monday was found dead at home, apparently due to natural causes. They also were looking for an evacuee missing since he told a friend he wanted to sneak back in.

Residents were urged to be patient by Billy See, the incident commander of that fire.

“When the smoke starts to clear, all the residents get very restless about trying to get back in and wanting to know when the evacuation orders and warnings will be lifted,” See said.

Some Firefighters Were Shuttled to Northern California After Battling Earlier Fires in Southern California

Authorities were working on a strategic plan for repopulating areas after ensuring that conditions were safe and there that there would be water service and electrical power for residents, he said.

The massive fires — coming much earlier in the season than expected — have pushed firefighters to the breaking point as they dealt with complications from the coronavirus pandemic and a lack of inmate crews who assist firefighters.

Some firefighters were shuttled to Northern California after battling earlier fires in Southern California.

Tim Edwards, president of the union representing state firefighters, said 96% of the state’s resources are committed to fighting the blazes. He was with a three-man fire engine crew that had traveled more than 400 miles (643 kilometers) from southern Riverside County to help fight wildfires in wine country north of San Francisco.

“Between the fires in Southern California and these, they’ve been going nonstop,” he said. “Fatigue is really starting to set in, but they’re doing it.”

Since Aug. 15, hundreds of fires have burned nearly 2,000 square miles (more than 5,000 square kilometers), an area roughly the size of Delaware.

The blazes have killed at least seven people, burned about 1,500 homes and other buildings, and prompted evacuation orders that still affect about 140,000 people.

David Serna, 49, a firefighter with the Presidio of Monterey Fire Department, was battling a fire in that county when his rented home in Santa Cruz County burned to the ground.

“I wanted to get up to the house and see what was left. Got up there and nothing. It was all gone,” Serna told KTVU-TV.

He and his wife did find a metal heart-shaped decoration from their wedding day.

“All the years that I fought fires and seeing this type of destruction in other places,” Serna said. “But when it hits that close to home, it becomes almost unbelievable.”

About 300 National Guard Troops Were Finishing Firefighter Training and Were Expected to Be on the Lines Wednesday

In the city of Vacaville, between San Francisco and Sacramento, 76-year-old Art Thomas said he found only ashes and melted metal at the site of the home he built with his own hands in a rural area where he had lived for 32 years.

“Possessions dating back to when I was a kid were all in the house, everything is gone,” Thomas said. “Between sad, crying, laughing — every emotion is there.”

He said he had left with his wife, two dogs and a pair of shorts and tennis shoes.

With limited crews to tackle fires on the ground, California has been relying more on bulldozers, aircraft and firefighters from other states and the federal government, said Daniel Berlant, chief of wildfire planning and engineering for the state Department of Forestry and Fire Protection, known as Cal Fire.

About 300 National Guard troops were finishing firefighter training and were expected to be on the lines Wednesday as another 300 begin four days of training, said spokesman Lt. Col. Jonathan Shiroma.

California has scrambled in recent years to field enough prison fire crews as their numbers dwindled while the state released lower-level inmates. Thousands more were released early as the state responded to the coronavirus pandemic.

A dozen inmate firefighting camps that had been forced to shut down in June for two-week quarantines because of the coronavirus are back in operation but the total of 43 camps are operating at about 40% of capacity, said corrections department spokesman Aaron Francis.

The challenge remains, however, as California heads into the fall. That’s when searing weather and dry gusts have historically sparked some of the largest and deadliest fires.