INDIAN FALLS, Calif. (AP) — Erratic winds and the potential for dry lightning added to the challenges facing firefighters battling California’s largest wildfire, one of numerous fires burning Monday across the U.S. West.

Over the weekend, the massive Dixie Fire merged with the smaller Fly Fire and tore through the remote Northern California community of Indian Falls. The fire had already leveled at least 16 houses and other structures, but a new damage estimate wasn't immediately available because flames were still raging in the mountain area.

What You Need To Know

  • California’s largest wildfire merged with a smaller fire and destroyed homes in remote areas with limited access for firefighters

  • Meanwhile, numerous other fires gained strength and threatened property across the U.S. West

  • The massive Dixie Fire had already leveled a dozen houses and other structures when it tore through the tiny community of Indian Falls after dark Saturday
  • Gov. Gavin Newsom declared a state of emergency for four northern counties

“Fire behavior has been so unpredictable, it hasn’t been safe for inspectors to go in to work,” said Mitch Matlow, a fire spokesman. “Until things settle down, we won't know the extent of what's burned.”

Flames spread in remote areas with steep terrain crews can’t easily reach, Matlow said. Gusty winds also hindered containment efforts and the problem could get worse with the predicted arrival later Monday of pyrocumulus clouds — literally meaning “fire clouds” — which can bring lightning and the risk of new ignitions.

Fire officials said the fire had charred nearly 309 square miles (800 square kilometers) of timber and brush in Plumas and Butte counties, about two hours northeast of Sacramento. It was 22% contained and more than 10,000 homes were still under threat.

Authorities were hopeful that improving weather will help them continue to make progress against the nation’s largest wildfire, the Bootleg Fire in southern Oregon. It was 53% contained after scorching 640 square miles (1,657 square kilometers) of remote land. On Monday, an additional crew of Oregon National Guardsmen were sent to help out the more than 2,200 people battling the fire.

The lightning-caused fire has burned at least 70 homes, mainly cabins, and some 2,000 residences were under evacuation orders.

In Montana, four firefighters were released from a hospital and a fifth was being treated at a burn center Monday after a wildfire overran them last week, authorities said. The five were building a defensive line at the Devil’s Creek Fire in Garfield County when winds shifted suddenly and blew flames back at them.

The firefighter still being treated — a U.S. Fish and Wildlife Service employee — “is making good progress and is in good spirits,” spokesperson Kari Cobb said.

Crews were trying to keep the 10-square-mile (26-square-kilometer) fire from reaching Fort Peck Reservoir along the Missouri River in central Montana. It's one of three major fires in the state.

Firefighters have frequently dealt with perilous fire behavior, with flames consuming huge areas of vegetation each day. Such conditions are often from a combination of unusual random, short-term and natural weather patterns heightened by long-term, human-caused climate change. Global warming has made the West much warmer and drier in the past 30 years.

Across the West this summer, firefighters have confronted an unusually large number of unpredictable early season fires, U.S. Forest Service Chief Randy Moore said.

He recalled a recent small fire in the Lava Beds area of California that firefighters thought they had doused, only to have the fire flare up again after it burned through a system of tree roots and travelled beneath a containment line.

“It’s off the charts in terms of how some of these fires are behaving,” Moore said.

Elsewhere in California, the 106-square-mile (275-square-kilometer) Tamarack Fire south of Lake Tahoe continued to burn through timber and chaparral but firefighters made progress, aided by cooler weather. The fire was 54% contained and evacuation orders that affected some 2,000 residents in 15 communities on both sides of the California-Nevada state line had been lifted. The fire, sparked by lightning July 4 in Alpine County, California, has destroyed at least 23 buildings, including more than a dozen in Nevada.

In north-central Washington, firefighters battled two fires in Okanogan County that threatened hundreds of homes and again caused hazardous air quality conditions over the weekend. And in northern Idaho, east of Spokane, Washington, a small fire near the Silverwood Theme Park prompted evacuations Friday evening at the park and in the surrounding area. The theme park was back open with the fire half contained.

More than 85 large wildfires were burning across the country, most of them in Western states. They had burned over 2,343 square miles (6,068 square kilometers) of land.