With another heat wave on the horizon, firefighters battling blazes on grassy slopes and deep in forest canyons across the state were in a frantic fight to gain ground.

The biggest battle was going on outside Yosemite National Park, where more than 2,700 firefighters have been lugging hoses and hand tools up rugged forest terrain alongside bulldozers while water- and retardant-dropping aircraft have roared overhead trying to contain the Ferguson fire.

The fire started July 13 and claimed a firefighter’s life in its first day when a bulldozer tumbled down a hillside during the building of a defensive line. The flames have pushed south and east along a south fork of the Merced River, but along the way they’ve crawled over ridge tops and into groves of dead wood east of Yosemite.

“What we have is a sea of standing dead timber,” said Jacob Welsh, a spokesman assigned to the blaze. “Whenever a tree snag gets fire in it, it could fall down. That catches others on fire. That’s the challenge.”


Crews have been preparing defensive positions ahead of the fire’s path and preparing other areas for burn operations that would eliminate potential fuel. In the last few days, the flames have reached the groves of dead pines that were victims to California’s brutal drought and massive bark-beetle infestation that have killed tens of millions of trees in recent years.

In those patches of land, crews aren’t just watching out for fire, but falling trees or branches, Welsh said.

“Everywhere that’s burning you hear trees falling in the distance,” he said. “They basically catch fire, they weaken, they fall. It’s definitely not a good deal when you’re on the ground and you hear that.”

The U.S. Forest Service estimates that since 2010, more than 129 million drought-stressed and beetle-ravaged trees have died across 7.7 million acres of California forest, mostly in the Sierra. Authorities have said the beetle epidemic is rapidly killing trees in the 4,500-foot to 6,000-foot elevation band of the central and southern Sierra range. It could take centuries for the trees to repopulate, if they ever do.


The Yosemite blaze is one of several huge fires that have burned across the state in recent weeks, including two west of Sacramento and one on the California-Oregon border. Homes were lost earlier this month in fires in Goleta in Santa Barbara County and near Alpine in San Diego County.

For the Ferguson fire, mandatory evacuations remain in place on Incline Road and in Jerseydale, Mariposa Pines, Cedar Lodge, Indian Flat Campground, Savage’s Trading Post, Sweetwater Ridge and the El Portal Trailer Court. The cause of the fire is under investigation. The blaze had consumed 22,892 acres and was 7% contained Friday morning.

In addition to the firefighter who was killed, two have been hurt battling the blaze.

Farther south in Riverside County, a brush fire that triggered evacuations in the Corona area on Thursday did not grow overnight, allowing firefighters to build up defensive lines that they expected to hold on Friday, officials said.


Dubbed the Skyline fire, the blaze near Cleveland National Forest remained at 250 acres Friday morning and was only 5% contained. But despite that low percentage, some 1,500 homes that were previously considered threatened no longer are, said Corona Fire Department spokesman Ryan Rolston.

That’s because crews worked through the night using hand tools, bulldozers and fire-retardant-dropping aircraft to build a defensive line around nearby foothill communities, Rolston said.

“There are a few areas that we don’t have line on it, but we’re going to focus on getting retardant drops,” he said.

At least 240 personnel are fighting that blaze, which started about 3 p.m. at Skyline Drive and Burrero Way, near the entrance to a hiking trail.


The wind-driven fire pushed near homes on Thursday, fueled by high heat, low humidity and gusty winds, Rolston said. The conditions overnight into Friday morning were markedly better, allowing crews to stage their defenses, he said. By the time afternoon winds push the flames out of the steep forest canyons, firefighters will be ready, he said.

Mandatory evacuations remained in place for Mabey Canyon and the Orchard Glen communities, but all others that had been issued Thursday were lifted.

The fire is burning in an unincorporated area of Riverside County, west of the city of Corona, county Fire Department spokeswoman April Newman said.

Firefighters from Cal Fire Riverside, the U.S. Forest Service and Corona are involved. At least 46 engine companies, six air tankers and four helicopters are being used.


Temperatures in Southern California are expected to surge beginning this weekend, with the mercury hitting 100 and beyond in inland areas by Monday, according to the National Weather Service.

joseph.serna@latimes.com

For breaking California news, follow @JosephSerna on Twitter.

UPDATES:


6:50 p.m.: This report was updated with the latest details on the fires.

This article was originally published at 12:15 p.m.