For a moment, the first week of summer looked like the prelude to a vicious fire season in the Bay Area , with blazes ripping through the hillsides south of Livermore and the ridges bordering Port Costa .
But firefighters managed to quash these fires quickly, aided by tame winds and a landscape still moist enough to keep the flames from spreading fast.
“It’s hot, but it’s not super windy,” Dwight Good, assistant chief of Cal Fire’s Santa Clara unit, told The Chronicle. “The humidities and the field moistures are still high enough to keep things manageable.”
From June 19 through 27, Cal Fire battled 14 major fires across the state that torched 10 acres or more, nine of them in the greater Bay Area region stretching from Sonoma County to the San Joaquin Valley in the east and south in the Santa Cruz mountains.
Good’s unit alone fought 25 fires of varying sizes, including the Tesla Fire which charred 524 acres in the Altamont area of Livermore. Cal Fire’s San Mateo-Santa Cruz unit responded to eight brush fires within the same time period, and assisted other agencies with seven fires.
While the number of conflagrations has dropped slightly statewide compared to last year — from 3,784 as of June 24, 2021, to 3,311 as of June 27, 2022 — last week’s spate of incidents seemed to usher in a sense of familiar apprehension in the Bay Area, where cell phones bleated evacuation orders and motorists encountered thick clouds of smoke on Interstate 280 and Highway 4 .
The breakneck pace for Cal Fire’s Santa Clara unit, which averaged more than three fires a day last week, has become normal for June, Good said. This year’s summer solstice arrived baked in triple-digit temperatures, followed by a round of monsoon rains and lightning strikes in the San Benito county area , before the region settled into its more typical pattern of sunshine and fog.
Despite those dramatic fluctuations, some indicators of fire danger have been less severe this year than in 2021, according to John Abatzoglou, an associate professor at UC Merced who researches climate and weather.
A few light rains and periods of respite between heat waves have kept the landscape from getting too arid, he said, and the clustering of fires near urban areas — while threatening — has also made it easier for crews to get the upper hand. The large infernos that tear through remote wildnerness “are given a head start,” he said.
Warren Blier, science officer at the National Weather Service’s Bay Area office, also credited mild winds and humidity for helping keep scores of wildfires at bay last week. He noted that many of the larger, out-of-control fires ignite at times when the air is parched, the wind is violent and the land is tinder-dry, conditions that can arise after weeks of roasting in torrid summer heat.
The Wine Country Fires that burned vast swaths of the Napa and Sonoma valleys in October, 2017 erupted after summer turned to fall, a time of year when the foliage is crackly and brittle. A dry atmosphere and gusty winds played a much bigger role in fueling those wildfires than the outside temperature, which was moderate for autumn the night the flames exploded, Blier said.
While climate change has redefined California’s seasons so dramatically that wildfires are now a year-round phenomenon, climate and weather alone don’t determine the path or intensity of a fire. The Wine Country fires were more dangerous because they sparked at night, when it was harder to deploy crews and evacuate residents, Blier said. Last week’s string of fires seemed to flare up during the day, when they were easier to control.
Fires also tend to be less daunting in early summer because crews are less fatigued, Good said, and more people are available to respond.
The biggest factor, however, is human behavior. People, and their infrastructure, cause the vast majority of fires, and were probably largely to blame for the cluster scalding the Bay Area in June.
“It’s poor judgment, bad luck, or bad habits,” Good said. “A vehicle backfiring. A flat tire. A trailer dragging chains. Illegal fireworks. A gender-reveal party. Someone running their lawnmower in knee-high grass in the middle of the afternoon.”
Blier agreed. “As is widely known, there really are only two sources of ignition,” he said: Lightning and people.
Fire experts constantly warn California residents to be more vigilant, given how this year’s fire season is shaping up.
“The book on California’s 2022 fire season is still being written,” Abatzoglou said. And in most parts of the state, the brush and grass are still damp, and the high winds haven’t yet arrived.