This autumn brought something that isn’t always common for much of California — a decent amount of rain in October. Rather than heat waves, there have been umbrellas.
After years in which some of the worst wildfires in state history happened in the fall, a lot of people are wondering: Is fire season over?
It depends on where you live, fire experts say. And simply put, there’s more risk in Southern California right now than Northern California.
“We have not yet seen enough rain in Southern California to end fire season,” said Daniel Swain, a climate scientist with the University of California division of Agriculture and Natural Resources. “But we probably have in Northern California.”
January saw historic, devastating fires in Los Angeles. Since then, it has been a relatively mild fire year statewide in California.
Through Monday Oct. 27, a total of 522,372 acres have burned statewide in areas overseen by Cal Fire and the U.S. Forest Service. That’s a drop of 40% from the previous 5-year average of 1.3 million acres over the same time. A big part of the reason is the early onset of rain.
Through Thursday, San Jose had received 2 inches of rain, more than four times its historical average for the month of October. Oakland had 1.64 inches — double its historical average of .84. Sacramento’s total also was double the historical average, and Santa Rosa and San Francisco were at 125% at 113% of normal for the month.
Farther south, Fresno was at 223% of normal, with 1.18 inches, and Los Angeles had received 252% of normal with 1.41 inches. But a few areas, including San Diego and Palm Springs, remain below normal. And nearly all of Southern California’s rain came in one storm on Oct. 15. After that, temperatures have soared back up, hitting 97 in Los Angeles this week.
On Wednesday the National Weather Service issued a red flag warning for parts of Ventura and Los Angeles counties. With forecasts for strong winds that day, Gov. Gavin Newsom announced that 129 firefighters, 10 engines and three helicopters would be pre-positioned in case fires started in those areas.
But in Northern California, the trend has been just the opposite.
Cal Fire cancelled a controlled burn planned for Wednesday at the Soquel Demonstration Forest aimed at reducing overgrown brush. The reason: brush and trees were too damp.
The day before, Cal Fire officials had planned to burn 52 acres in San Mateo County in a controlled fire east of Interstate 280 near Belmont and Crystal Springs Reservoir. They gave up after 6 acres because only grass and not heavier vegetation like coyote brush would burn, said Sarah Collamer, a Cal Fire forester who was overseeing the operations.
“We’re still in fire season,” she said. “We are getting small starts. They are going until we put them out. But the fire danger is greatly reduced.”
Illustrating her point, last Thursday, a fire broke out east of downtown San Jose at Alum Rock Park. Cal Fire sent a plane to drop retardant on it. But it was put out at 10 acres and caused no damage. A grass fire that began near Altamont Pass in Alameda County last Sunday burned 20 acres and was easily contained by fire crews.
Moisture levels are key. As most campers know, wet wood doesn’t burn. When California is in droughts and heat waves, moisture levels in plants plummet. After rains and cooler temperatures, along with higher humidity levels, moisture levels go up. Then, fires may start in grass, but they don’t spread easily to damp brush and trees, particularly if there aren’t strong winds.
“Right now you could get a grass fire going,” said Craig Clements, director of the Fire Weather Lab at San Jose State University. “But whether or not it will end up being a big fire is unlikely. We are seeing the hills green up already from the early rain. It looks like January right now in the East Bay Hills.”
Overall, national experts say California is in good shape. The 7-day forecast from the National Interagency Fire Center in Boise, Idaho has “little or no fire risk” for all of California except part of southern California from Santa Barbara to the Mexican border where it is listed as “low risk.” And more rain is forecast in Northern California on Wednesday.
Fire experts disagree on whether there is an exact amount of rain each fall that signals the end of fire season. Often, supervisors of controlled burns wait until at least 1 inch has fallen, Clements said.
Dan Cayan, a research meteorologist with the Scripps Institution of Oceanography in San Diego, published a study in 2022 showing that since World War II, 90% of the acres burned in Southern California have burned before .35 of an inch of rain has fallen in autumn. After that, fires can still start during winter dry spells and high Santa Ana winds, he said. But they are much less likely.
“Northern California is doing pretty well,” he said. The dividing line this fall between wetter-than-normal and drier-than-normal runs through L.A. County. We’ve had some slight rain in San Diego, but it has been nearly three weeks with nothing. We’re still in a vulnerable situation down here.”
Many of California’s worst wildfires have occurred in the fall, including the Oakland Hills Fire in October 1991; the Camp Fire in Paradise, in November 2018; and the Tubbs Fire in October 2017, which killed 22 people and burned 5,600 structures in Napa and Sonoma counties.
After those fires, Cal Fire officials and many political leaders began saying that fire season is all year long in California due to warmer conditions from climate change.
To some extent that is true. The devastating wildfires in Pacific Palisades and Altadena this year occurred in January, amid a long, hot, dry spell and winds that reached 100 mph.
But in general, risk goes down when rains start, temperatures cool, and days shorten, experts say. Because of the damp weather this fall, Cal Fire officials have begun to relax back-yard burning rules. Starting Oct. 17, they have allowed it in nearly every Bay Area County and all counties north to the Oregon border, under permits, when it was altogether illegal during the hot summer months.
In winter, Cal Fire stations also reduce staffing from peak levels, although that has not started yet.
“We could still have 80-degree days with winds,” said Capt. Robert Foxworthy, a Cal Fire statewide spokesman. “There’s still a chance of wildfire. We’re not expecting large damaging, destructive fires burning timber and brush because of how much moisture we’ve received. But in some places there is a threat still there.”
