SAN FRANCISCO — Two of the three largest fires in California history, burning simultaneously in the Santa Cruz Mountains and in wine country north of San Francisco Bay, are expected to grow in the next few days as a new thunderstorm system moves over the northern half of the state, producing dry lightning and gusty winds.

The National Weather Service initially issued red-flag warnings across large swaths of Northern and Central California through Monday afternoon. With firefighters already responding to more than two dozen major fires, it was feared the storms could ignite even more blazes and cause existing ones to spread more rapidly, pushing crews into a triage situation.

However, forecasters canceled the red-flag warning covering the Bay Area and northern Central Coast shortly after 9:30 a.m. Pacific time Monday, saying that “weak cells are still over the North Bay; however, most moisture has moved north of our area and instability has decreased, giving us confidence to let the warning expire early.”

Firefighters also were able to use a brief respite in the wind over the weekend to build containment lines.

Crews battling the CZU Lightning Complex fire in San Mateo and Santa Cruz counties got some additional help from Mother Nature in the form of rain showers Sunday evening.

“The weather hasn’t been as significant as we were expecting, which is good,” Mark Brunton, operations chief for the California Department of Forestry and Fire Protection, or Cal Fire, said at a briefing Monday morning. “And that has given us an opportunity for our crews to make a lot of great progress throughout this fire.”

But the sheer magnitude of what has already burned is sobering: about 1.3 million acres this month alone, with four more months of potential fire season to go. Only 2018 saw more land scorched in California – over an entire year.

Now it’s clear that what Californians had feared most during this long, troubled summer has become reality: a terrible fire season in the middle of the COVID-19 pandemic.

“I’m essentially at a loss for words to describe the scope of the lightning-sparked fire outbreak that has rapidly evolved in Northern California – even in the context of the extraordinary fires of recent years,” wrote Daniel Swain, a climate scientist at the University of California, Los Angeles, in a blog post. “It’s truly astonishing.”

On Saturday, Gov. Gavin Newsom announced that the White House had approved California’s request for a presidential major disaster declaration to bolster the state’s emergency response to the wildfires.

Across California, “over 14,000 firefighters are on the front lines of more than two dozen major fires and lightning complexes,” or groups of fires, Jeremy Rahn, Cal Fire public information officer, said at a Sunday media briefing.

There have been more than 13,000 lightning strikes statewide since Aug. 15, he added Monday, and “an astonishing 2,700 more wildfires have occurred this year than last, with an additional 1.4 million acres burned in the same time period.”

The blazes include the LNU Lightning Complex fire, which at nearly 350,000 acres is the second-largest fire in California history. The SCU Lightning Complex fire, at more than 347,000 acres, is the next largest.

Combined, they dwarf the Thomas fire, which at 281,893 acres shattered the records just three years ago.

“To have both of those going on at the same time … gives us the magnitude of what has happened here in this state,” Sean Kavanaugh, incident commander on the LNU fire, said Sunday.

The LNU fire complex in Napa, Sonoma, Lake, Solano, Yolo and Colusa counties had killed five people, destroyed 871 homes and other buildings and was 22 percent contained as of Monday morning. The fire was threatening the communities from the coastal redwoods around Guerneville to the dry grass ravines around Vacaville on the edge of the Central Valley, more than 50 miles east.

“The size and complexity of this fire is not one that we’ve seen in times past,” Cal Fire Unit Chief Shana Jones said during a briefing Monday, adding that “everyone on the line is extremely tired but working so incredibly hard.”

She pointed out that “we have a few more months of fire season” left in California, so residents should make sure they’re prepared to evacuate should the need arise.

The SCU Lightning Complex fire began as a collection of about 20 blazes in areas of Contra Costa, Alameda, Santa Clara, Stanislaus and San Joaquin counties and by Sunday had merged into two conflagrations.

The fires, which were 10 percent contained as of Monday morning, were burning primarily through grass and brush in steep, remote areas that hadn’t burned in years.

“There’s a lot of dead fuel up there,” said Barbara Rebiskie, public information officer on the SCU fire. “And the erratic winds, the 7 percent humidities and the lightning – it’s not a good combination.”

As of Monday morning, an estimated 20,065 homes and commercial buildings were threatened and 12 structures had been destroyed.

A new evacuation order was issued at 3 a.m. Sunday for parts of Alameda County. In the hours that followed, a public information center was flooded with so many phone calls that it crashed.

While firefighting resources have been pouring into the region in recent days, officials say it’s simply not enough.

In some places, officials said, they were being turned down for state help and left to beg for equipment and manpower from volunteers and local agencies.

“Many of these firefighters have been on the lines for 72 hours, and everybody is running on fumes,” said Democratic Assemblyman Jim Wood of Healdsburg, whose district includes the wine country areas under siege. “Our first responders are working to the ragged edge of everything they have.”

With the number of fires overwhelming the available crews, state officials are being forced to prioritize which incidents will get resources and focus on saving lives and structures at the expense of trying to contain the fires. That means some of the blazes could burn for weeks.

“At the statewide level, we do get into this mode where we start wondering where the biggest loss is going to be, what’s the highest priority, and that is where the resources are going to go,” said Lenya Quinn-Davidson, a fire specialist with the UC Cooperative Extension.

What had forecasters most concerned Sunday afternoon was an area of moisture with the potential to generate thunderstorms that was just off Central California and moving toward the Monterey area, said Carolina Walbrun, a meteorologist with the National Weather Service in Monterey.

The front was expected to continue to move north, affecting a stretch of the state from Monterey to the Bay Area, she said. A second event was forecast Monday night into Tuesday.

“The fear that we have as these thunderstorms develop is that it can create strong downdrafts and result in further fire spread,” Walbrun said. “We also have the potential of generating additional fires with dry lightning from these thunderstorms. There’s very little moisture associated with it.”

The system was expected to cause winds to shift to more of a southwesterly direction, moving the flame fronts with it.

“The issue that is going to hamper this whole thing is going to be the lack of resources that are available for firefighting because there are so many fires active right now,” she said. “All resources are depleted. So any additional starts are just going to stress the system even more.”

Since late July, more than 1,100 homes, commercial buildings and other structures have been destroyed by fires in California, with nearly all of that destruction occurring after Aug. 15, which marked the start of what officials are calling a “lightning siege” of about 12,000 strikes that started an estimated 585 fires in California.

The CZU Lightning Complex fire was threatening multiple communities and had forced 77,000 people from their homes. The blaze began as a collection of about 22 fires that largely merged into one, challenging firefighters as they tried to keep the flames away from the towns dotting the rural, mountainous area.

The fire had consumed 78,000 acres and was 13 percent contained as of Monday morning. It threatened 24,323 structures and had destroyed 231.

The body of a 70-year-old man was recovered in the fire area, according to Santa Cruz County Sheriff’s Chief Deputy Chris Clark.

Clark said the man’s body was found “some distance away” from what appeared to be his vehicle near the end of Last Chance Road. He said it looked as though the man was “likely leaving the fire.”

Authorities are still searching for four people who have been reported missing.

Firefighters were taking advantage of fairly calm winds to attack the fire on the ground as much as possible as they scrambled to make progress ahead of the expected storm, said Daniel Potter, a Cal Fire public information officer.

“We’re going to get as much accomplished as we can before the front hits us,” he said. “And then adapt and overcome any new fires that may start in the area due to the lightning coming through.”

Crews were working to establish containment lines and fire breaks around the city of Santa Cruz and the campus of UC Santa Cruz in a bid to keep the blaze from damaging the community if it made a run in that direction.

“It’s pretty much impossible to stop when a good wind is pushing the fire front faster than we can move,” Potter said.

As of Monday morning, Clark said there was “no imminent fire danger” to Santa Cruz.

Officials were asking people to stay out of evacuation zones to avoid hazards, including fire and downed trees and wires, and to keep roads open for emergency vehicles.

“It is highly dangerous in there still. There are trees coming down. We have redwood trees, old-growth timber that is coming across the roadway and we have infrastructure that needs repair,” Jonathan Cox, a deputy chief with Cal Fire, said Monday. “We have bridges that have failed. … It is not safe.”

While the intense firefight continues in and around the Bay Area, crews have made significant progress on several other substantial wildfires throughout the state.

The Lake fire, which ignited near Lake Hughes in Los Angeles County on Aug. 12, is now 62 percent contained, officials said Monday. That blaze has charred more than 31,000 acres and destroyed 33 structures and outbuildings.

Elsewhere in L.A. County, the Ranch 2 fire is now 81 percent contained, officials said Monday. That wildfire has burned 4,237 acres near Azusa.

The River fire, burning south of Salinas in Monterey County, is now 23 percent contained. That 48,424-acre wildfire has destroyed 21 structures since it started Aug. 16.

Crews also reported 15 percent containment for the Carmel fire, which is burning nearby to the southwest. That fire has consumed roughly 6,700 acres and destroyed 51 structures.

Comments are not available on this story.