SUNSANVILLE (CBS SF/AP) — Crews slowed the wall of flames advancing toward Janesville early Tuesday, but with winds predicted to pick up, temperatures to soar, humidity levels to plunge and lightning in the forecast later this week, the battle with the massive Dixie Fire is far from easing.

There was some good news. Plumas County Sheriff Todd Johns said four residents reported missing in the wake of the destruction of Greenville have been found safe.

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The blaze stood at 487,764 acres and was 25 percent contained. There were more than 5,000 firefighters on the fire lines which stretched more than 465 miles, the equivalent of traveling from Chico to Los Angeles.

The fire is the largest single wildfire in California history and 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.

Deputy Incident Commander Chris Waters said officials were only confident that about 20% of those lines were secure.

“Every bit of that line needs to be constructed, staffed, mopped up and actually put to bed before we can call this fire fully contained,” Waters said.

It was a message echoed on Monday night by Fire Incident Commander Rocky Opliger.

“We have angry fire on a landscape that makes it very difficult to contain these fire, control these fires,” he said.

Early Tuesday, the firefighters battling the advance toward Janesville were being aided by previously charred land still recovering from the 2020 Sheep Fire and the 2019 Walker Fire, which consumed 54,612 acres near Genesee Valley in the Plumas National Forest approximately 11 miles east of the community of Taylorsville.

DIXIE FIRE: 

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.

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“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.

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 triple-digit 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. So far 873 structures have been destroyed with several hundred of those homes.

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’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.

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