• Firefighters face 38C heat and strong winds, complicating containment efforts
• Arson suspect charged, held without bail for starting Park Fire
• More than 4000 people evacuated, some returning home as containment reaches 27%

More than 6000 firefighters in California’s Central Valley continued to battle the largest blaze in the United States, which burned its way into the history books as the state’s fourth-largest conflagration on record.

There was barely a taste of rain from thunderstorms that brought wind and rainfall of zero to one-tenth of an inch, forecasters said.

The heat of 38C with winds up to 40.2km/h or more in some spots, offered little relief to the firefighters trying to contain the Park Fire, scorching the wilderness terrain 160km north of Sacramento, the state capital.

“We had some thunderstorms that just brought us down-drafts, that’s a problem,” said Christopher Young, a spokesman for the California Department of Forestry and Fire Protection, or Cal Fire. “Lightning is a factor we worry about.”

Blazes from the Park Fire, started by an alleged arsonist who pushed a flaming car down an 18m gully near Chico, California, on July 24, has since burned more than 162,200ha or more than 1553sq km, an area larger than the city of Los Angeles.

The 42-year-old man arrested had not entered a plea, but was charged with arson and held without bail, officials said.

More than 560 homes and other structures were destroyed since the blaze started 11 days ago, feeding off downed timber and tinder-dry grass and brush. The fire was 27% contained, officials said.

More than 4000 people were evacuated including retiree Jim Young, 65, of Red Bluff, where he lived in a trailer home with his dog, Sparky.

He and the dog spent the last eight days camped out with some other families in a gravel lot at a wilderness trailhead about 9.5km from his home, worrying every day if it was safe.

“We just found out we can go home,” Young said. “Our property is safe. So many lost everything. But me and Sparky can go home now.”

The rough, wilderness terrain means it takes two to three hours to reach the fire lines, officials said. Some firefighters are being flown to the front lines by helicopters, with some expected to stay there for days with supplies also flown in.

The national wildfire season has had an intense start, raising the risk of stretching firefighting resources too thin. The National Interagency Fire Centre has already requested help from firefighters in Australia and New Zealand, who will arrive from Thursday NZT and deploy to Oregon and Washington.