Firefighters battle to contain California's largest wildfire of the summer, a blaze near famed Yosemite National Park that has forced thousands of people to evacuate.

Some 2,500 firefighters backed by 17 helicopters have been deployed against the Oak Fire, which has forced around 3,000 people to evacuate.
Some 2,500 firefighters backed by 17 helicopters have been deployed against the Oak Fire, which has forced around 3,000 people to evacuate. (AFP)

US firefighters have finally started to control California's largest wildfire so far this year, halting its eastward expansion toward nearby Yosemite National Park while thousands of people remained under evacuation orders.

Several officials with the California Department of Forestry and Fire Protection (Cal Fire) said on Monday the fire initially behaved unlike any other they had seen, with burning embers sparking smaller fires up to three kilometres in front of the main conflagration.

But firefighters have not seen more of that so-called spotting, Cal Fire spokesperson Natasha Fouts said from the incident command centre in Merced, about 210 kilometres inland from San Francisco.

The absence of other major fires in the region enabled Cal Fire to concentrate 2,500 firefighters on the blaze, and the lack of wind allowed for the continuous use of aircraft to drop water and fire retardant, officials said.

"It was a perfect storm of a good kind," said Hector Vasquez, a Cal Fire spokesperson, at the command post in Mariposa, California, closer to the fire.

The northward direction of the fire was taking it into the Sierra National Forest but no longer in the direction of Yosemite, some 16 kilometres away. A grove of Yosemite's giant, ancient sequoia trees did come under threat from another wildfire weeks ago.

The Oak Fire expanded rapidly since it began on Friday, overwhelming the initial deployment of firefighters, as extremely hot and dry weather fueled its galloping pace through dry forest and underbrush.

It grew to 16,791 acres by Monday morning, an increase of 1,200 acres overnight and more than half the size of San Francisco, Cal Fire said.

The fire had more than doubled in size from Saturday to Sunday. It was 10 percent contained on Monday compared to zero on Sunday.

READ MORE: Thousands evacuated as 'explosive' California wildfire widens

'Challenging and extremely dangerous'

Since starting on Friday, the fire has chased more than 3,700 people from their homes. The fire has destroyed seven residential structures, officials said, revising down a previous figure of 10.

High temperatures in the area on Monday were expected to reach 37 Celsius with a slight breeze throughout the day.

The current fire pales in comparison to last year's Dixie Fire, which burned nearly one million acres.

"What we're seeing on this (Oak Fire) is very indicative of what we've seen in fires throughout California, in the West over the last two years," Jon Heggie, a Cal Fire battalion chief, told CNN.

"These fires are burning with just such a velocity and intensity it makes it extremely challenging and extremely dangerous for both the public and the firefighters," Heggie said.

More than two decades of drought and rising temperatures have conspired to make California more vulnerable than ever to wildfires, with the two most devastating years on record coming in 2020 and 2021, when more than 6.8 million acres burned, an area greater than the size of Rwanda. 

READ MORE: US authorities order evacuation as wildfire spreads in California

Source: TRTWorld and agencies