Firefighters on Monday 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.

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.

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

But firefighters have not seen more of that so-called spotting, Cal Fire spokesperson Natasha Fouts said on Monday from the incident command center in Merced, about 130 miles (210 km) 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 10 miles (16 km) away. A grove of Yosemite's giant, ancient sequoia trees did come under threat from another wildfire weeks ago.

The Oak Fire grew to 16,791 acres (6,795 hectares) 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% contained on Monday compared to zero on Sunday.

Since starting on Friday, the fire has chased more than 3,700 people from their homes. Wes Smith, a Mariposa County Sheriff Department officer and his wife Jane lost their home of 37 years, their son Nick wrote on a GoFundMe page.

"It is devastating to lose everything literally in the blink of an eye without notice," he wrote.

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 98 degrees Fahrenheit (37 Celsius) with a slight breeze throughout the day.

A 20% chance of thunderstorms was in the forecast on Monday night and Tuesday morning, the National Weather Service said. Otherwise the area could expect 100-degree weather much of the week.

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 (2.75 million hectares) burned, an area greater than the size of Rwanda.