SALEM, Ore. – A heat wave and the potential for lightning threatened the Pacific Northwest and Northern California on Thursday as firefighters battling multiple wildfires prepared for the chance of new blazes igniting.
Parts of Washington, Oregon and Northern California were under heat advisories or excessive heat warnings Thursday, and temperatures were expected to top 100 degrees over the next few days.
"It won't be as hot as what we saw a month ago, but it's still going to be pretty hot," National Weather Service meteorologist John Bumgardner said.
The heat wave at the end of June caused hundreds of deaths in Oregon, Washington and British Columbia, Canada.
In much of southern Oregon and parts of Northern California, a red flag warning was in place as lightning strikes "will likely result in new fire starts," the weather service said.
More on the June heat wave: Record-breaking Pacific Northwest heat wave blamed for 107 deaths in Oregon
Gusty thunderstorms are expected and could cause fires to spread.
"The system is expected to drop rain," Bumgardner said. "The question will be whether it falls everywhere there are strikes and if it moves slow enough to prevent the fires that might be ignited."
Half a dozen fires burning in Oregon have scorched more than 780 square miles. Across the West, there are 82 large fires burning 2,500 square miles in 13 states, according to the National Interagency Fire Center.
More than 21,500 wildland firefighters and support personnel are battling the fires.
The Bootleg Fire in Oregon, the third-largest in state history, has burned more than 645 square miles since it was ignited by lightning in early July. The almost 2,000 firefighters working on the fire have it 53% contained.
Though rain this week helped stall the flames, the U.S. Forest Service said much of the dry vegetation that is the fire's fuel rebounded quickly. "Heavy concentrations of fuels became active in the afternoon, highlighting the extreme resistance to extinguishment," the Forest Service said.
Though the storms may have helped with one blaze, Umpqua National Forest saw 40 dry lightning strikes this week that ignited 21 fires.
At the California-Nevada border Wednesday, Govs. Gavin Newsom and Steve Sisolak called for more federal firefighting assistance as they toured the damage from the Tamarack Fire south of Lake Tahoe.
“We need help on the federal side. We need more people coming in. We need more resources. We need more air support. We need more boots on the ground,” Nevada Gov. Sisolak said.
Western wildfires: Residents urged to conserve energy as conditions worsen
Newsom acknowledged the role climate change has played in making wildfires more frequent and intense. "The world is radically changing as the climate changes. You may not believe in science, you got it with your own damn eyes,” he said, gesturing toward the blackened landscape.
The Pinnacle Fire in Monterey County ignited Thursday, burning 100 acres near Pinnacles National Park, according to the California Department of Forestry and Fire Protection (Cal Fire). The fire prompted closures to the western entrance and hiking trails in the park, and its cause remains under investigation.
Fire activity also picked up Thursday in the Dixie Fire, the largest burning in the Golden State. Cal Fire said higher temperatures and lower humidity caused the increased blaze in the eastern part of the fire, which is burning in Northern California between Lassen National Forest and the town of Paradise.
Crews made progress fighting the flames by air Thursday, Cal Fire said, but they expected conditions to worsen as the weather grows warmer, according to the Forest Service.
The fire has burned more than 345 square miles and is 23% contained, according to Cal Fire.
Elsewhere, a southeastern Montana wildfire exploded in size, threatening numerous homes as it burned through grasslands and sage brush around the Crow Indian Reservation near the Wyoming border, officials said Thursday. The fire that started Tuesday in the Poverty Flats area outside the reservation has grown to at least 86 square miles (222 square kilometers), according to an official estimate released Thursday.
Australia sent a jet airtanker to the United States to help fight wildfires, the National Interagency Fire Center said Wednesday. The jet was made available through an agreement between the U.S. Department of Agriculture and Australia.
“We greatly appreciate having this airtanker from the New South Wales Rural Fire Service assisting us,” said Kim Christensen, deputy assistant director for operations for the Forest Service. “We’re proud of the long history of cooperation we have with Australia and other countries.”
Urness reported from Salem, Oregon.
This article originally appeared on USA TODAY: Fire update: Heat wave, storms may spark wildfires in Oregon, Calif.