Cal Fire Battalion Chief Jon Heggie wasn’t expecting much to worry about when a late summer fire erupted north of Santa Cruz, home to California’s moist and cool “asbestos forests.” This place doesn’t burn, he thought, with just three notable fires there in 70 years.

Heggie’s job was to predict for the crews where the wildfire might go and when, working through calculations based on topography, weather and fuels — the “immutable” basics. For fire behavior analysts like Heggie, predictable and familiar are manageable, while weird and unexpected are synonyms for danger.

But that 2020 fire was anything but predictable.

Around 3 a.m. on Aug. 16, ominous thunder cells formed over the region. Tens of thousands of lightning strikes rained down, creating a convulsion of fire that became the CZU Lightning Complex.

By noon there were nearly two dozen fires burning, and not nearly enough people to handle them. Flames were roaring throughout the Coast Range in deep-shaded forests and waist-high ferns in sight of the Pacific Ocean. No one had ever seen anything like it. The blaze defied predictions and ran unchecked for a month. The fire spread to San Mateo County, burned through 86,000 acres, destroyed almost 1,500 structures and killed a fleeing resident.

“It was astonishing to see that behavior and consumption of heavy fuels,” Heggie said. “Seeing the devastation was mind-boggling. Things were burning outside the norm. I hadn’t seen anything burn that intensely in my 30 years.”

Almost as troubling was what this fire didn’t do — it didn’t back off at night.

“We would have burning periods increase in the afternoon, and we saw continuous high-intensity burns in the night,” Heggie said. “That’s when we are supposed to make up ground. That didn’t happen.”

“Seeing the devastation was mind-boggling. Things were burning outside the norm. I hadn’t seen anything burn that intensely in my 30 years.”
— John Heggie, Cal Fire battalion chief

That 2020 summer of fires, the worst in California history, recalibrated what veteran firefighters understand about fire behavior: Nothing is as it was.

Intensified by climate change, especially warmer nights and longer droughts, California’s fires often morph into megafires, and even gigafires covering more than a million acres. U.S. wildfires have been four times larger and three times more frequent since 2000, according to University of Colorado researchers. And other scientists recently predicted that up to 52% more California forest acreage will burn in summertime over the next two decades because of the changing climate.

As California now heads into its peak time for wildfires, even with last year’s quiet season and the end of its three-year drought, the specter of megafires hasn’t receded. Last winter’s record winter rains, rather than tamping down fire threats, have promoted lush growth, which provides more fuel for summer fires.

Cal Fire officials warn that this year’s conditions are similar to the summer and fall of 2017 — when a rainy winter was followed by one of the state’s most destructive fire seasons, killing 47 people and destroying almost 11,000 structures.

US Forest Service teams deploy drones to capture photographs and infrared images, which are used to map fires to find areas where flames are still active and where they might spread. Photo by Andrew Avitt, US Forest Service

It’s not just the size and power of modern wildfires, but their capricious behavior that has confounded fire veterans — the feints and shifts that bedevil efforts to predict what a fire might do and then devise strategies to stop it. It’s a dangerous calculation: In the literal heat of a fire, choices are consequential. People’s lives and livelihoods are at stake.

Cal Fire crews now often find themselves outflanked. Responding to larger and more erratic and intense fires requires more personnel and equipment. And staging crews and engines where flames are expected to go has been thrown off-kilter.

“We live in this new reality,” Gov. Gavin Newsom said at a recent Cal Fire event, “where we can’t necessarily attach ourselves to some of the more predictive models of the past because of a world that is getting a lot hotter, a lot drier and a lot more uncertain because of climate change.”

CalFire has responded by tapping into all the new technology — such as drones, military satellites, infrared images and AI-assisted maps — that can be brought to bear during a fire. Commanders now must consider a broader range of possibilities so they can pivot when the firefront shifts in an unexpected way. The agency also has beefed up its ability to fight nighttime fires with a new fleet of Fire Hawk helicopters equipped to fly in darkness.

“We live in this new reality. ..We’re enlisting cutting-edge technology in our efforts to fight wildfires, exploring how innovations like artificial intelligence can help us identify threats quicker and deploy resources smarter.”
— Gov. Gavin Newsom

The state has thrown every possible data point at the problem with its year-old Wildfire Threat and Intelligence Integration Center, which pulls information from dozens of federal, state and private sources to create a minute-by-minute picture of conditions conducive to sparking or spreading fires.

“We’re enlisting cutting-edge technology in our efforts to fight wildfires,” Newsom said, “exploring how innovations like artificial intelligence can help us identify threats quicker and deploy resources smarter.”

An unforeseen assault on a coastal town

The 2017 Thomas Fire stands as an example of what happens when a massive fire, ignited after a rainy winter, veers and shifts in unexpected ways.

The blaze in coastal Ventura and Santa Barbara counties struck in December, when fire season normally has quieted down. Fire veterans knew fall and winter fires were tamed by a blanket of moist air and fog.

But that didn’t happen.

“We were on day five or six, and the incident commander comes to me and asks, ‘Are we going to have to evacuate Carpinteria tonight?’,” said Cal Fire Assistant Chief Tim Chavez, who was the fire behavior analyst for the Thomas Fire. “I looked at the maps and we both came to the conclusion that Carpinteria would be fine, don’t worry. Sure enough, that night it burned into Carpinteria and they had to evacuate the town.”

Based on fire and weather data and informed hunches, no one expected the fire to continue advancing overnight. And, as the winds calmed, no one predicted the blaze would move toward the small seaside community of 13,000 south of Santa Barbara. But high temperatures, low humidity and a steep, dry landscape that hadn’t felt flames in more than 30 years drew the Thomas Fire to the coast.

“I looked at the maps and we both came to the conclusion that Carpinteria would be fine, don’t worry. Sure enough, that night it burned into Carpinteria and they had to evacuate the town.”
—Tim Chavez, Cal Fire Assistant Chief

The sudden shift put the town in peril. Some 300 residents were evacuated in the middle of the night as the blaze moved into the eastern edge of Carpinteria.

In all, the fire, which was sparked by power lines downed by high winds, burned for nearly 40 days, spread across 281,000 acres, destroyed more than 1,000 homes and other buildings and killed two people, including a firefighter. At the time, it was the largest wildfire in California’s modern history; now, just six years later, it ranks at number eight.

The unforeseen assault on Carpenteria was an I-told-you-so from nature, the sort of humbling slap-down that fire behavior analysts in California are experiencing more and more.

“I’ve learned more from being wrong than from being right,” Chavez said. “You cannot do this job and not be surprised by something you see. Even the small fires will surprise you sometimes.”

Warmer nights, drought, lack of fog alter fire behavior

Scientists say the past 20 years have brought a profound — and perhaps irreversible — shift in the norms of wildfire behavior and intensity. Fires burn along the coast even when there’s no desert winds to drive them, fires refuse to lay down at night and fires pierced the so-called Redwood Curtain, burning 97% of California’s oldest state park, Big Basin Redwoods.

The changes in wildfires are driven by an array of factors: a megadrought from the driest period recorded in the Western U.S. in the past 1,200 years, the loss of fog along the California coast, and stubborn nighttime temperatures that propel flames well into the night.

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