California fires: What to expect in the coming months

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  • BOULDER CREEK, CA - August 22: Firefighters work to protect homes surrounding residences engulfed in flames on Madrone Avenue at the corner of Virginia Avenue before 2 a.m. in Boulder Creek, Calif., on Friday, August 22, 2020. (Dylan Bouscher/Bay Area News Group)

  • BIG BASIN, CA - AUGUST 28: Lumberman Jason Vincent looks at the base of a redwood tree that toppled during the CZU Complex fire in Big Basin Redwoods State Park, Friday, Aug., 28, 2020, near Boulder Creek, Calif. Vincent was in the park felling damaged Douglas fir trees before they could potentially damage other redwoods. (Karl Mondon/Bay Area News Group)

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  • LAKE BERRYESSA, CA - AUGUST 27: Artist Marcia Ritz, 77, looks through the rubble of her manufactured home at the Spanish Flat Mobile Villa trailer park in Lake Berryessa, Calif., on Thursday, Aug. 27, 2020. The Hennessey Fire, part of the LNU Lightning Complex Fire, tore through the area on Aug. 18. Ritz and her husband Jerry Rehmke, 80, rode out the fire with nine other people aboard a pontoon boat as flames surrounded Lake Berryessa. (Jane Tyska/Bay Area News Group)

  • BIG BASIN, CA - AUGUST 28: Will Christianson and Jason Vincent clear away fallen brush from the base of the Mother of the Forest redwood as hot spots from the CZU Complex fire continue burning in Big Basin Redwoods State Park, Friday, Aug., 28, 2020, near Boulder Creek, Calif. (Karl Mondon/Bay Area News Group)

  • LAKE BERRYESSA, CA - AUGUST 27: A deer is seen near a destroyed home in the Berryessa Highlands neighborhood in unincorporated Napa County, Calif., on Thursday, Aug. 27, 2020. The Hennessey Fire, part of the LNU Lightning Complex Fire, tore through the area on Aug. 18. (Jane Tyska/Bay Area News Group)

  • BOULDER CREEK, CA - August 22: Flames engulf a home on the 17000 block of Big Basin Highway on Friday, Aug. 22 2020. (Dylan Bouscher/Bay Area News Group)

  • BONNY DOON, CA - AUGUST 27: A charred truck from the CZU Lightning Complex Fire sits on Empire Grade in Bonny Doon, Calif., on Thursday, Aug., 27, 2020. (Ray Chavez/Bay Area News Group)

  • WINTERS, CA – AUGUST 20: The LNU Lightning Complex wildfire burns a hillside behind the Canyon Creek Resort in Winters, Calif., early Thursday morning, Aug. 20, 2020. (Anda Chu/Bay Area News Group)

  • SWANTON, CA - AUGUST 28: Roots of trees continuing burning which makes trees to get weaker and fall down on the roads after the CZU Lightning Complex Fire burned vegetation and structures in Swanton, Calif., on Friday, Aug., 28, 2020. Access to this road still not open to the public due to precarious conditions. (Ray Chavez/Bay Area News Group)

  • LAKE BERRYESSA, CA - AUGUST 27: A smoky sunset is seen through the chimney of a destroyed home from the fire-ravaged Berryessa Highlands neighborhood in unincorporated Napa County, Calif., on Thursday, Aug. 27, 2020. The Hennessey Fire, part of the LNU Lightning Complex Fire, tore through the area on Aug. 18. (Jane Tyska/Bay Area News Group)

  • LAKE BERRYESSA, CA - AUGUST 27: A fire-destroyed home is seen in the Berryessa Highlands neighborhood in unincorporated Napa County, Calif., on Thursday, Aug. 27, 2020. The Hennessey Fire, part of the LNU Lightning Complex Fire, tore through the area on Aug. 18. (Jane Tyska/Bay Area News Group)

  • MIDDLETOWN, CA - AUGUST 26: Fountain Valley firefighters watch as helicopters make air drops while the Hennessey Fire, part of the LNU Lightning Complex Fire, flares over a ridge line near the Cal Fire helicopter base on Butts Canyon Road in Middletown, Calif., on Wednesday, Aug. 26, 2020. (Jane Tyska/Bay Area News Group)

  • LAKE BERRYESSA, CA - AUGUST 27: An American flag flies above a Trump 2020 flag in the fire-damaged Berryessa Highlands neighborhood in unincorporated Napa County, Calif., on Thursday, Aug. 27, 2020. The Hennessey Fire, part of the LNU Lightning Complex Fire, tore through the area on Aug. 18. (Jane Tyska/Bay Area News Group)

  • BOULDER CREEK, CA - August 22: Firefighters work to protect homes surrounding residences engulfed in flames on Madrone Avenue at the corner of Virginia Avenue before 2 a.m. in Boulder Creek, Calif., on Friday, August 22, 2020. (Dylan Bouscher/Bay Area News Group)

  • LAKE BERRYESSA, CA - AUGUST 27: A statue of a bull is seen by a destroyed home in the Berryessa Highlands neighborhood in unincorporated Napa County, Calif., on Thursday, Aug. 27, 2020. The Hennessey Fire, part of the LNU Lightning Complex Fire, tore through the area on Aug. 18. (Jane Tyska/Bay Area News Group)

  • MIDDLETOWN, CA - AUGUST 26: A waxing gibbous moon rises as the Hennessey Fire, part of the LNU Lightning Complex Fire, flares over a ridge line near the Cal Fire helicopter base on Butts Canyon Road in Middletown, Calif., on Wednesday, Aug. 26, 2020. (Jane Tyska/Bay Area News Group)

  • BIG BASIN, CA - AUGUST 28: Jason Vincent walks inside a giant redwood tree felled by the CZU Complex fire in Big Basin Redwoods State Park, Friday, Aug., 28, 2020, near Boulder Creek, Calif. Vincent was cutting down damaged Douglas fir trees in the park before they could fall on their own, potentially damaging other redwoods. (Karl Mondon/Bay Area News Group)

  • LAKE BERRYESSA, CA - AUGUST 27: A smoky sunset is seen from the fire-ravaged Berryessa Highlands neighborhood in unincorporated Napa County, Calif., on Thursday, Aug. 27, 2020. The Hennessey Fire, part of the LNU Lightning Complex Fire, tore through the area on Aug. 18. (Jane Tyska/Bay Area News Group)

  • SWANTON, CA - AUGUST 28: An excavator operator removes fallen trees from Swanton Road after the CZU Lightning Complex Fire burned vegetation and structures in Swanton, Calif., on Friday, Aug., 28, 2020. Access to this road still not open to the public due to precarious conditions. (Ray Chavez/Bay Area News Group)

  • MIDDLETOWN, CA - AUGUST 26: Emergency personnel and residents watch as helicopters make air drops as the Hennessey Fire, part of the LNU Lightning Complex Fire, flares over a ridge line near the Cal Fire helicopter base on Butts Canyon Road in Middletown, Calif., on Wednesday, Aug. 26, 2020. (Jane Tyska/Bay Area News Group)

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California has already had a historic year for wildfires.

So far, 1.66 million acres have burned — an area five times the size of the city of Los Angeles. Almost no part of the state is untouched. From the Santa Cruz Mountains to Riverside County, the slopes of Mount Hamilton to Napa Valley and the northern Sierra, 15,800 firefighters from as far away as Florida and New Jersey are battling two dozen major fires, many sparked by rare lightning storms two weeks ago.

And although fire crews are finally gaining the upper hand on many, fire experts have a stark message: This year is particularly dry, and the worst could still be to come.

“We’re just now approaching the peak of fire season,” said Daniel Berlant, a spokesman for Cal Fire, the state’s primary firefighting agency.

There are at least two, and potentially three more months left where the risk of huge new fires will continue to grow until the fall rains arrive. And 2020 has already seen the second-most acres burned of any year in modern history, behind only 2018, when 1.97 million acres burned.

“It is so important that we get the public’s help,” Berlant said. “We have been incredibly busy these last two weeks. These have been Mother Nature-sparked fires. We need people to reduce the risk of human-sparked fires.”

An analysis of fall rainfall patterns over the last decade tells the tale.

Using San Francisco as a proxy for Northern California, in seven of the past 10 years, the first significant rainstorm of half an inch or more didn’t occur until after Nov. 15. That’s 11 weeks from now. In the other three years, the earliest it arrived was Oct. 16. That’s seven weeks away.

“We are sort of holding our breath until we get into the rainy season right now,” said Jan Null, a meteorologist with Golden Gate Weather Services in Half Moon Bay, who combed through the data.

“Just because the current events are starting to wind down doesn’t mean we aren’t going to see more fires,” he said. “We are heading into what is normally the most dangerous part of fire season.”

BOULDER CREEK, CA – AUGUST 19: Volunteer firefighters for the Boulder Creek Fire District look at the direction of the fire before they are dispatched to battle the CZU August Lightning Complex fire on Aug. 19, 2020, in Boulder Creek, Calif. (Dai Sugano/Bay Area News Group) 

The past explains the future.

Eight of California’s 10 deadliest fires of all time have occurred in October or November, from the Camp Fire that killed 85 people in the town of Paradise in 2018 to the Wine Country Fires in Napa and Sonoma counties in 2017, to the Oakland Hills Fire in 1991.

Similarly, seven of the 10 most destructive fires in California history, measured by the number of homes burned, occurred in October or November.

There are two primary reasons, experts say: lack of rain and strong, dry winds.

Unlike in most other states, it almost never rains in the summer in California. As part of California’s Mediterranean climate, most rain ends in April every year, and apart from a few light sprinkles, doesn’t begin again in earnest until November. That means by the time October arrives, nearly six months have passed without rain.

As a result, grass, shrubs and trees are usually at their driest condition of the year in October.

Records show that most of California’s worst fire seasons, ranked by acres burned, come after the state has had a drier-than-normal winter. Why? More snow falls in the Sierra Nevada in wet winters. The longer it lasts into the summer, the less area there is to burn. And more rain means more moisture in the vegetation.

Unfortunately, this year was a dry winter.

On April 1, the statewide Sierra snowpack was just 54% of its historical average. Last year it was 161%, and California ended up with a below-average fire year, where just 259,148 acres burned statewide.

The same story is true with rainfall. Since Oct. 1, San Francisco has received just 50% of its historic average rainfall, San Jose 49%, Oakland 42% and Sacramento 53%. Los Angeles and San Diego, by contrast, have had a normal rainfall year, getting 101% and 133% of their historic averages.

Simply put, conditions are drier than normal in Northern California, which contributed to the explosive spread of this month’s CZU, SCU and LNU fires.

Craig Clements, director of the Fire Weather Research Laboratory at San Jose State University, called the mid-August lightning storms, which caused 12,000 lightning strikes and sparked roughly 700 new fires, a rare event. California hasn’t seen anything like it since 2008. People shouldn’t read too much into it as a predictor of the rest of the year, he said. Instead, they should look at the broader rainfall patterns, combined with a heatwave much of the state endured just before the fires, and daily measurements, like overnight humidity.

“It’s crazy we had so many ignitions all at once,” Clements said. “It’s apocalyptic for a lot of people. But it was a freak weather event. Let’s hope this was the big event for the year.”

Huge amounts of dead brush, trees and other vegetation, some killed during the state’s five-year drought and some piled up due to decades of fire suppression, are also making fires burn hotter and bigger.

Clements and his students regularly sample the amount of water in chamise, a common flowering shrub, to determine fuel moisture levels.

At Quail Hollow Ranch County Park in the Santa Cruz Mountains near Ben Lomond, they found the moisture level of chamise on Aug. 16 was 67%. That’s where it was last year in mid-September. In other words, brush and other vegetation in the Santa Cruz Mountains, which are still burning, are as dry now as they were a month later in the year last year.

“We’re seeing fuel moisture levels that are equivalent to our drought years,” he said. “Because we probably won’t get rain in the next few weeks, these fuels are going to continue to be dry. And they are already critical.”

Climate change is also playing a role. The 10 hottest years globally back to 1880 when modern temperature records began all have occurred since 1998, according to NASA and NOAA, the parent agency of the National Weather Service. Hotter weather dries out vegetation earlier in the year, leading to a longer fire season.

Add to that strong “Santa Ana” winds in Southern California and “Diablo” winds in Northern California, which blow hot inland air across the state, increase fire risk and typically peak in October.

FAIRFIELD, CA – AUGUST 19: A Cal Fire tanker drops fire retardant on a hillside behind homes in the Rolling Hills neighborhood of Fairfield, Calif., on Wednesday, Aug. 19, 2020. Residents were ordered to evacuate as the LNU Lightning Complex wildfire threatened the neighborhood. (Anda Chu/Bay Area News Group) 

“We have a lot of fire season ahead of us. We’re calling it the fire year,” said Robert Baird, director of fire and aviation management for the U.S. Forest Service’s Pacific Southwest Region in Vallejo. “People shouldn’t let their guard down.”

Baird, whose own family was evacuated two weeks ago for a night from their house near Vacaville due to the LNU Complex Fire, said people all over the state should clear vegetation from around their homes, and draw up an evacuation plan and a list of items they would take if they had to leave suddenly due to an encroaching blaze.

“People need to watch red flag warnings as if they were tornado warnings,” he said. “They are a murderous combination of dry air, wind and heat. They can be killers, and have killed people.”

“When there’s fire on the ground,” he warned, “it’s too late to make your preparations.”

U.S. Forest Service firefighters clear debris from a steep hillside while fighting the Dolan Fire in Big Sur on Tuesday Aug. 25, 2020. (David Royal/ Monterey Herald Correspondent)