The trees, grass and brush were so dry that "if an ember lands, you're virtually guaranteed to start a new fire," Matlow said. The blaze was running parallel to a canyon area that served as a chimney, making it so hot that it created enormous pyrocumulus columns of smoke. These clouds bring chaotic winds, making a fire "critically erratic" so it's hard to predict the direction of growth, he added.
Dawn Garofalo fled with a dog and two horses from a friend's property near Greenville, and watched the soaring cloud grow from the west side of Lake Almanor. "There's only one way in and one way out," she said. "I didn't want to be stuck up there if the fire came through."
From her campsite on the dry lake bed, she watched the fire glowing on the horizon before dawn. To the south, Cal Fire said between 35 and 40 homes and other structures burned in the fast-moving River Fire that broke out Wednesday near Colfax, and within hours swelled to more than 2 square miles (5 square kilometers). There was no containment and thousands of people are under evacuation orders in Placer and Nevada counties.
And about 150 miles (240 kilometers) to the west of the Dixie Fire, the lightning-sparked McFarland Fire threatened remote homes along the Trinity River in the Shasta-Trinity National Forest.
The fire was only 5% contained after burning through nearly 25 square miles (65 square kilometers) of drought-stricken vegetation.
Similar risky weather was expected across Southern California, where heat advisories and warnings were issued for interior valleys, mountains and deserts for much of the week. Heatwaves and historic drought tied to climate change have made wildfires harder to fight in America's West.
Scientists say climate change has made the region much warmer and drier in the past 30 years and will continue to make weather more extreme and wildfires more frequent and destructive.
More than 20,000 firefighters and support personnel were battling 97 large, active wildfires covering 2,919 square miles (7,560 square kilometers) in 13 U.S. states, the National Interagency Fire Center said.
