GLEN ELLEN, Calif. — Hundreds of sleep-deprived, stubble-faced firefighters, their yellow coats layered with soot, assembled here Wednesday to hear their commanders say what they already knew: The fires that have devastated California’s wine country were still spreading, nowhere near containment, and the crews battling the blazes were stretched to their limits.
“I wish I could say the cavalry is coming — it’s not,” Battalion Chief Kirk Van Wormer of Cal Fire, the state firefighting agency, told the gathering of firefighters, flecks of ash raining down on them. “Look to your left and look to your right. Those are the people you are responsible for right now.”
Fanned by warm, dry winds, the fires have grown so big, so fast, that the immediate goal fire officials set was not so much to stop the spread as to slow it, to channel it away from threatened cities and towns, and to save lives. Saving homes and businesses was secondary.
The fires have killed at least 29 people in Northern California, officials said on Thursday. Fifteen of the deaths were in Sonoma County. Officials cautioned that the figures could rise as emergency workers are able to return to scorched areas and search for hundreds of people who have been reported missing.
Robert Giordano, the Sonoma County sheriff, said, “So far, in the recoveries, we have found bodies that were almost completely intact, and we have found bodies that were nothing more than ash and bones.” In some cases, he said, the only way to identify the victims was by the serial numbers stamped on artificial joints and other medical devices that were in their bodies.
Statewide, there were 21 major fires burning on Thursday, having consumed more than 191,000 acres since the outbreak began on Sunday night, said Ken Pimlott, the chief of Cal Fire, the state firefighting agency. The number of separate fires rises and falls often, as new blazes flare up and old ones merge with one another, but the size of the devastated area has grown steadily.
In the hardest-hit region, in Napa and Sonoma Counties, the sun was an orange dot in a leaden haze. There were eight major blazes there on Thursday, and the burned area grew to more than 120,000 acres, Cal Fire reported. The agency said that the 34,000-acre Tubbs Fire, which has burned parts of the city of Santa Rosa and has threatened Geyserville, was 10 percent contained, but most of the other blazes in wine country were 3 percent contained or less.
Officials threw out sobering figures on the scale of the devastation, with the caveat that the numbers were just estimates, sure to rise when the crisis has abated enough to allow an accurate damage assessment. Thousands of structures have been destroyed, many more are threatened, and tens of thousands of people have been displaced.
“These fires are literally just burning faster than firefighters can run,” Mr. Pimlott said. Wind-whipped embers leapfrogged past the exhausted fire crews, he said, so “we are attacking many, many new fires that we put out while they are still small.”
Almost 8,000 state and local firefighters battled the blazes, using more than 550 fire engines, 73 helicopters and more than 30 airplanes, state officials said, with additional crews and 320 more fire engines en route from neighboring states and from federal agencies. But vast as the resources were, they clearly were not enough.
The standard practice in a California wildfire is for firefighters to work 24-hour shifts, and then have 24 hours off. But many firefighters in Sonoma and Napa have had no real rests for days, catching a few hours of sleep on the ground or in their trucks.
“We’ve got guys who have been working 80 hours straight,” said Capt. Sean Norman, the deputy head of operations for the Sonoma Valley fires. “You’ve got to have a fifth gear. You’ve got to have the two C’s: Commitment and caffeine.”
Giving units their assignments, he instructed them how to call in air tankers to drop water or fire retardant, and implored them to stay safe. “We don’t have the resources to anchor and defend,” Captain Norman told them.
With wind gusting from the north, fire crews primarily formed lines along the southern flanks of the fires, often carrying heavy gear through rugged terrain, trying to slow or stop the spread. They doused the flames and threatened vegetation with hoses, and firefighters and National Guard troops used bulldozers, shovels and axes to clear brush and trees, to create fire breaks.
With a major wildfire fanned by high winds, firefighters can often do little more than focus on saving lives, experts said. That can include performing a kind of triage, deciding which structures to save and which to let burn.
“The biggest part of the playbook is that you focus on public safety and not fighting the fire,” said J. Keith Gilless, dean of the College of Natural Resources at the University of California, Berkeley. “Your capacity on really extreme fire behavior — and this was really extreme fire behavior — is really quite limited. This is about as complex a situation as you are going to find.”
The wind defeats the usual strategy, to create a perimeter — a path around the fire that has been stripped of fuel — and then close in on the flames from there. If a fire is described as 10 percent contained, that means that 10 percent of the perimeter has been established. In Napa, the largest of the fires is described as only 3 percent contained.
“You have to just wait for Mother Nature to take a rest before you can flank the fire and put a perimeter around it,” said Bob Roper, a consultant and former fire chief in Ventura County, Calif. He added that ordinarily, fire commanders can call on resources from around the state to fight a major blaze, but having so many places in flames at once limits their ability to do that.
In Bennett Valley near Santa Rosa, a ranch owner had left the sprinklers on before fleeing, and even as a fire engulfed a nearby mountain and spread toward the ranch, black and white cows grazed in an untouched pasture nearby. A few firefighters doused the property perimeter, but within minutes, small, new patches of flame flared up; it had been like that for days, hindering progress, and making it impossible to defend each structure.
“The biggest thing is the sheer volume of fire we have,” said Kevin Burris, acting captain of the Petaluma Fire Department, who said the fires were the worst he had seen in 15 years on the job. Soot covered his face, and he said he had slept just five hours in the previous four days.
Mr. Van Wormer, the Cal Fire battalion chief, said optimal staffing for a fire of 20,000 acres is 1,000 firefighters. In Sonoma Valley, where more acreage than that has burned, he said there were 464 firefighters, including about 60 state prison inmates.
“We are not giving people rest,” he said. “Exhaustion is a huge problem.”
With no reports of lightning strikes in recent days, fire officials said their investigations are likely to conclude that human activity caused the fires. One possibility they are investigating is that power lines or other parts of the electrical grid ignited vegetation; a number of lines in the region went down, but it is not clear whether that happened before or during the burning.
In April, California’s Public Utilities Commission fined the Pacific Gas and Electric Company $8.3 million for failing to properly clear vegetation around a power line in the Sierra Nevada, sparking a fire in 2015 that burned more than 70,000 acres, killed two people, and destroyed 550 homes. The state has been trying to force the company to pay $90 million in firefighting costs.
Thomas Fuller reported from Glen Ellen, and Richard Pérez-Peña from New York. Henry Fountain and Hiroko Tabuchi contributed reporting from New York, and Adam Nagourney from Los Angeles.