One of California's biggest blazes of the year has forced locals to flee for their lives before their homes were destroyed. 

Residents of remote mountain communities near Yosemite National Park described the moments they realised their lives and homes were at threat. 

Rodney Maguire told television station KXTV that he had already lost his home, only saving a few possessions.

"I had just enough time to get birth certificates, my DB 214 (military discharge papers), the picture of my parents," he said. 

Mr Maguire is among thousands of residents who have been forced to evacuate since a fast-moving wildfire began on Friday within a kilometre from the Mariposa Pones township. 

By Sunday evening, the uncontained fire had consumed 6,314 hectares, more than half the size of Paris, according to the California Department of Forestry and Fire Protection (Cal Fire).

But it was still more than 16 kilometres from Yosemite, famed for its giant, ancient sequoia trees.

About 2,000 firefighters battled the blaze alongside aircraft and bulldozers, facing tough conditions that included steep terrain, sweltering temperatures and low humidity.

"It's hot out there again today," Cal Fire spokesperson Natasha Fouts said on Sunday.

"And the fuel moisture levels are critically low."

Crews on the ground protected homes as air tankers dropped retardant on 15-metre flames racing along ridge tops east of the tiny community of Jerseydale.

Light winds blew embers ahead into tree branches "and because it's so dry, it's easy for the spot fires to get established and that's what fuels the growth", Ms Fouts said.

Officials described "explosive fire behaviour" on Saturday as flames made runs through bone-dry vegetation caused by the worst drought in decades.

The cause of the fire was under investigation.

Evacuations were in place for over 6,000 people living across the Sierra Nevada foothills, though a handful of residents defied the orders and stayed behind, said Adrienne Freeman with the US Forest Service.

Local Jerry Cal told KXTV that he was under evacuation orders, but was not sure if he would go.

"This is our home. I feel like we're going to do what we can to at least have a chance," he said.

AP/Reuters