Progress made but hot weather could spur California's Dixie wildfire

California's largest single wildfire in recorded history kept pushing through forestlands as fire crews tried to protect rural communities from flames that have destroyed hundreds of homes.

Thick smoke cleared for several hours along one edge of the Dixie Fire on Monday, allowing aircraft to join nearly 6,000 firefighters in the attack. Many were battling to protect more than a dozen small mountain and rural communities in the northern Sierra Nevada.

"Today was the first day in a few days that we had good, clean air in there so we were able to use our helicopters," allowing some progress, Kyle Jacobson, the east zone incident commander, said at an evening briefing.

Crews managed to cut thousands of acres of new fire lines and the fire's southern edges were in good shape but the fire's future was an unknown, authorities said.

"We don't know where this fire is going to end and where it's going to land. It continues to challenge us," said Chris Carlton, supervisor for Plumas National Forest.

Heat to return

But high pressure building over the Western United States meant the weather would heat up and dry out again in the next few days, possibly hitting record high temperatures on Wednesday and Thursday along with a return of strong afternoon winds, fire meteorologist Rich Thompson warned.

Those are the conditions that have caused the fire to spread rapidly since it began on July 13. Burning through bone-dry trees, brush and grass, the fire had burned more than 600 homes and other buildings, incinerating much of the small community of Greenville. Another 14,000 structures were threatened.

Damage reports are preliminary because assessment teams can't get into many areas, officials said.

Even more troubling, monsoonal moisture coming up from the south could produce a chance of thunderstorms heading into the weekend that could bring dry lightning and gusts that produce a greater fire threat, Thompson said.

The fire had grown to an area of 1,950 square kilometres and was just 22 per cent contained, according to the California Department of Forestry and Fire Protection. It had scorched an area more than twice the size of New York City.

The Dixie Fire is about half the size of the August Complex, a series of lightning-caused 2020 fires across seven counties that were fought together and that state officials consider California's largest wildfire overall.

Four firefighters were taken to the hospital Friday after being struck by a fallen branch. More than 30 people were initially reported missing, but by Monday the Plumas County Sheriff's Office had accounted for all of them.

Historic drought

California's raging wildfires are among some 100 large blazes burning across 15 states, mostly in the West, where historic drought conditions have left lands parched and ripe for ignition.

The Dixie Fire was the largest wildfire burning in the U.S. Nearly a quarter of all firefighters assigned to Western fires are fighting California blazes, said Rocky Oplinger, an incident commander.

Heat waves and historic drought tied to climate change have made wildfires harder to fight in the American West. Scientists have said climate change has made the region much warmer and drier in the past 30 years and will continue to make the weather more extreme and wildfires more frequent and destructive. The fires across the West come as parts of Europe are also fighting large blazes spurred by tinder-dry conditions.

Under investigation

The fire's cause was under investigation. Pacific Gas & Electric has said it may have been sparked when a tree fell on one of its power lines. A federal judge ordered PG&E on Friday to give details by Aug. 16 about the equipment and vegetation where the fire started.

Northwest of the Dixie Fire in the Shasta-Trinity National Forest, hundreds of homes remained threatened by two fires that continued to grow. About a third of the McFarland Fire was contained. New evacuation orders were issued Monday for residents near the Monument Fire, which was only about 3% contained.

South of the Dixie Fire, firefighters prevented further growth of the River Fire, which broke out Wednesday near the community of Colfax and destroyed 68 homes.