LOS ANGELES — An ecologically sensitive portion of Joshua Tree National Park will be closed this week due to extreme wildfire risk as a heat wave is set to broil the region over the Fourth of July holiday.

The Covington Flats area, home to some of the park’s largest Joshua trees, junipers and pinyon pines, will be shut to the public Wednesday through Sunday, reopening Monday morning, according to the National Park Service. The remote area includes 10 miles of Park Service-maintained roads and access points to backcountry trailheads, officials said.

The closure comes after the August 2023 storm Hilary, followed by other storms in the fall and winter, stoked the growth of grasses, creating what experts call a continuous fuel bed connecting larger shrubs and trees. Those grasses, now dry, could help flames spread across the landscape, said Sasha Travaglio, park ranger at Joshua Tree National Park.

“These fuel conditions make it easy for a fire to start and hard to control if it becomes established,” Travaglio wrote in an email. “Fast-burning grasses can quickly spread fire to large plants like Joshua trees and juniper.” Those larger plants then burn longer and hotter, helping to sustain the fire, she added.

The grasses that have taken hold in the area include invasive species such as cheatgrass and Mediterranean grasses, which now fill the once-empty spaces of dirt that used to naturally exist between native desert plants, Travaglio said.

A warm spring and early summer have helped ensure the vegetation is ready to burn, said Ryan Worley, meteorologist with the National Weather Service in Phoenix. Historical climate data for the park are hard to come by, making it difficult to calculate average or record temperatures, he said. But most of the region has seen above-normal temperatures in June — it was the hottest June on record in Phoenix, he noted.

“It’s been very hot across the region for the month,” Worley said. “So we can’t say for certain if we saw a daily record broken in the park, but it’s very likely that temperatures were well above normal throughout the month of June.”

And more heat is on the way, thanks to a large area of high pressure that’s expected to develop at sea and move over the West Coast and Great Basin later in the week, Worley said. Temperatures are forecast to approach triple digits by Wednesday and continue to climb through the weekend, he said.

It’s reasonable to expect temperatures in the park to be eight to 10 degrees above normal for this time of year, as is forecast for elsewhere in southeastern California, he said. Conditions are also expected to be dry and, at times, breezy, with gusts that could reach 25 mph, he said.

“With those hot temperatures, very dry conditions and potentially gusty winds here and there, it looks like there could be some periods of elevated fire weather conditions in and around the park,” he said.

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