SAN FRANCISCO — Firefighters struggled against rugged terrain, high winds and an August heat wave Tuesday to slow the spread of the biggest wildfire ever recorded in California, an inferno that exploded to more than 450 square miles in just 11 days.
The blaze, centered near the community of Clearlake, about 100 miles north of San Francisco, spread fast because of what officials said was a perfect combination of weather, topography and abundant vegetation turned into highly flammable fuel by years of drought.
The flames were burning in mostly remote areas, and no deaths or serious injuries have been reported. But at least 75 homes have been lost, and thousands of people living near Clearlake have been forced to flee. The blaze, dubbed the Mendocino Complex, was reported 20 percent contained.
Its rapid growth to an area the size of Los Angeles at the same time firefighters were battling more than a dozen other major blazes around the state fanned fears that 2018 could become the worst wildfire season in California history.
“For whatever reason, fires are burning much more intensely, much more quickly than they were before,” said Mark A. Hartwig, president of the California Fire Chiefs Association.
About 3,900 firefighters, including a crew of 40 volunteers from New Zealand, were battling the blaze, contending with temperatures in the high 90s and winds gusting to 25 mph.
The area has few roads that can serve as firebreaks, and firefighters instead fell back to natural barriers like streams or used bulldozers to cut fire lines.
But the flames were moving so fast in spots that they blew past fire lines, forcing firefighters to retreat, said Battalion Chief Jonathan Cox of the state Department of Forestry and Fire Protection, or Cal Fire.
In all, 14,000 firefighters were battling blazes across California, which is seeing earlier, longer and more destructive wildfire seasons because of drought, warmer weather attributed to climate change, and the building of homes deeper into the forests.
“Cal Fire is really an urban firefighter service in the woods,” said Arizona State University professor Stephen Pyne, a wildfire management expert.
The Mendocino Complex is actually two blazes burning so close together that authorities are attacking them as one, a common practice at Cal Fire. The fires started July 27 within an hour of each other and about 15 miles apart. As of Tuesday, they were separated by just a few miles. Officials have not determined the cause of either one.
In becoming the biggest fire in California history, the Mendocino Complex fire broke a record set just eight months ago. A blaze in Southern California in December killed two people, burned 440 square miles and destroyed more than 1,000 buildings.
Crews also gained ground this week against another Northern California wildfire, one that destroyed more than 1,000 homes in and around the city of Redding and was blamed for at least six deaths.
California’s firefighting costs have more than tripled from $242 million in the 2013 fiscal year to $773 million in the 2018 fiscal year that ended June 30, according to Cal Fire.
“We’re in uncharted territory,” Gov. Jerry Brown warned last week. “Since civilization emerged 10,000 years ago, we haven’t had this kind of heat condition, and it’s going to continue getting worse. That’s the way it is.”