More than 6,000 firefighters in California's Central Valley continued to battle the largest blaze in the U.S. on Saturday, which burned its way into the history books as the state's fourth-largest conflagration on record.

There was barely a taste of rain on Saturday from thunderstorms that brought wind and rainfall of zero to one-tenth of an inch, forecasters said. The heat of 38 degrees Celsius along with winds up to 25 mph or more in some spots, offered little relief to the firefighters trying to contain the Park Fire, scorching the wilderness terrain some 161 kilometers 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."