“While good progress continues on the fire, much work remains to be done,” the update said. Many evacuation orders have been converted to fire advisories, officials said.
Some areas were inaccessible to bulldozers, so crews on foot cut into the fire line, and smoke from the fire hampered the response of the 24 helicopter units involved.
No firefighters have been injured since the fire started, and the cause remains under investigation.
More than 1,100 structures are under threat.
As of Tuesday morning, Cal Fire officials said in an overnight incident report: “Fire crews continue to provide structural protection, extinguish hot spots and establish and improve live lines. Continued drought, severe dry fuels and tree mortality continue to contribute to fire spread.”
More than 3,000 personnel, including two dozen helicopters, 286 fire engines, 68 water tenders and 94 bulldozers, are fighting the fire.
Challenging terrain and abundant dry vegetation are fueling the fire, which has complicated efforts to slow its growth, Cal Fire spokesman Cpt. Keith Wade told CNN Monday.
“The footprint here, the amount of fuel that burns when a fire burns, the available terrain — ravines, drainage — the wind that flows through these areas can make fire behavior erratic. To explode … the ferocity of that fire can be intense at times,” Wade said.
Cal Fire has reported 23 wildfires in California so far this month, but only three have exceeded 500 acres. None came close to the massive destruction of the Oak Fire, Wade said, because of extremely dry conditions in the area.
“The real difference that firefighters are experiencing here is how dry everything is, and it’s definitely been (dry) for years,” he said. “We noticed that there was less precipitation, less humidity, and the available fuel load was definitely out.”
The fire’s rapid growth has made evacuation efforts more difficult, Cal Fire Battalion Chief John Heggie told CNN on Monday, adding that officials and law enforcement officials are doing their best to notify residents when it’s time to evacuate.
“The reality is that it moves so quickly, it doesn’t give people a lot of time, and sometimes they have to leave with the shirt off their back,” Heggie said.
Cal Fire said progress made by fire crews has allowed officials to reduce evacuation orders to fire advisories in some areas.
An evacuation shelter has been set up at Mariposa Elementary School for displaced residents.
Heggie attributed the “speed and intensity” of the Oak Fire to the state’s prolonged drought and human-caused climate change.
“I can tell you this is a direct result of climate change,” he said. “You can’t have a 10-year drought in California and expect things to stay the same. And we’re paying the price for that 10-year drought and climate change right now.”
“That dead fuel and drought that resulted from climate change is driving these, what we now call ‘megafires,'” Hecki said.
“It is time to learn to live with fire,” the report suggested, urging authorities and policymakers to collaborate with local communities to use indigenous knowledge and invest in planning and prevention efforts.
CNN’s Poppy Harlow, Taylor Romine, Stella Chan, Sarah Smart and Rachel Ramirez contributed to this report.
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