Big fall storm for California: What this means for fire risk

SACRAMENTO, Calif. — A large well-organized weather system is beginning to come together with moderate to major impacts expected throughout California by early next week.

This storm will bring some of the biggest rain and snow totals the state has seen since March, prompting some to wonder how this will shift fire risk.

The state spans nearly 800 miles north to south and covers multiple different climates from the redwoods of Humboldt County to the deserts of Imperial. 

David Acuña, Cal Fire Battalion Chief in the communication program, says California’s diverse geography makes fire planning complex. Cal Fire addresses that complexity by dividing the state into 21 units covering 52 of its 58 counties, each able to tailor strategies to local conditions.

Acuña reminds us fire season is year-round and says “fall presents a couple of extra elements.” The two key elements are weather conditions and fuel moisture.

One of the biggest threats this time of year comes from offshore winds like Santa Ana or Diablo. These are dry, warming winds and can spread fires faster than responding agencies can contain them. Cal Fire works closely with the National Weather Service to assess risks like these wind events but also for lightning activity, dry conditions and recent rainfall. 

“If it’s recently rained, it’s not going to immediately turn green,” Acuña said. 

Vegetation will absorb some of that moisture, but the critical factor is the frequency of storms and how quickly it dries out.

This is why Cal Fire has to take into account each storm and how it’s impacting everything from grass to trees. Acuña explains fuels are categorized by how long it takes them to gain or lose moisture. The smallest, “one-hour” fuels, like dry grass, can ignite easily after only an hour of low humidity. Larger fuels such as brush or manzanita hold moisture longer, while massive fuels like pines or redwoods take months without rain to fully dry out.

The difference can be crucial when fall storms are few and far between. 

“That’s why we don’t refer to fire seasons anymore,” Acuña said. “We refer to the fire year.” 

Even if heavier vegetation remains hydrated, lighter grasses can act as “ladder fuels,” carrying flames into the canopy where major fires can spread.

Cooler weather can also be deceptive. Acuña points to the January 2025 fires in Southern California when temperatures in the 70s and 80s still fueled dangerous conditions largely because extremely dry fuel conditions were met with a wind event.

This is why rainfall plays a role in reducing fire danger, but its effect can vary. Acuña says Cal Fire is preparing to reopen burn permits in parts of Northern California that saw light precipitation. But he says even in those zones, microclimates can stay dry enough to spark a wildfire. 

“If we get a wind, which is aligned with topography… there can still be a significant fire,” Acuña said.

Fire risk isn’t tied to the calendar, and neither is Cal Fire’s staffing. The agency is working with the Legislature to make more firefighters permanent. The agency responds to not just wildland fires, but medical emergencies, vehicle crashes, hazardous materials incidents and technical rescues.

Cal Fire is also expanding, with plans to grow to more than 14,000 personnel by 2027. This would be the largest staff on record. 

“We’re already more than twice the size that we were just seven years ago,” Acuña said. 

The department is now the second-largest fire agency in the nation, behind the New York City Fire Department.

Acuña said the agency’s regional coordination centers move crews around the state depending on where the threat is greatest. When Northern California faces dry lightning while southern California remains damp, resources shift north — and vice versa.

Even after major fires, Cal Fire assists with flood and recovery efforts alongside Cal OES. 

“Anything that falls within serving and safeguarding the people, property and resources of California is our responsibility,” Acuña said.

As the state heads deeper into fall, Acuña encouraged residents to use the relative lull to prepare. At ReadyForWildfire.org, people can find guides on creating go-bags, evacuation plans and escape routes. The department’s main site, fire.ca.gov, tracks all fires over 10 acres and provides evacuation and shelter information.

“Being ready for wildfire means being ready for any emergency,” Acuña said.

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