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After ballooning in size over the weekend, the US Forest Service (USFS) reported that Idaho’s Moose Fire had spread to 40,000 acres on Thursday.

The fire was 15% contained and more than 870 personnel were assigned to the incident.

The cause of the wildfires has not yet been determined, but hot and dry conditions continue across the western US

An increase in thunderstorms and erratic fire behavior has led to a temporary fire weather watch.

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The threat continues Friday, and the USFS has issued a severe lightning warning.

Residents in Carmen and North Fork were ordered to evacuate.

The Idaho Mountain Express reported that smoke from the Moose Fire has affected air quality in the Lemhi, Sawtooth and Wood River basins.

The Moose Fire burning Bobcat Gulch in North Fork, Idaho

The Moose Fire burning Bobcat Gulch in North Fork, Idaho
(Credit: Marilyn Davis, Public Information Officer via US Forest Service – Salmon-Chalice National Forest)

The incident comes a week after a firefighting helicopter that crashed into the Salmon River killed both pilots.

Thomas Hayes, 41, of Post Falls, Idaho, and Jared Byrd, 36, of Anchorage, Alaska, died when their CH-47D Series “Chinook” went down.

The “highly experienced” pilots were employees of Anchorage-based ROTAK Helicopter Services, which had been contracted. Help fight the Moose Fire.

Hayes and Byrd were also military veterans.

California’s largest wildfire of the year has burned near Yosemite

An air tanker releases retardant as it tries to stop the Oak Fire from advancing in Mariposa County, California, Sunday, July 24, 2022.

An air tanker releases retardant as it tries to stop the Oak Fire from advancing in Mariposa County, California, Sunday, July 24, 2022.
(AP Photo/Noah Berger)

As fires continue to burn across the western US, firefighters have made progress on a California wildfire near Yosemite National Park.

Officials eased some evacuation orders for nearby residents.

The Oak Fire in Mariposa County has spread to more than 18,800 acres and was 36% contained Wednesday.

The weather there was expected to be hotter and drier for the next two days.

Firefighters clear hot spots as they battle the Oak Fire in the Jerseydale community of Mariposa County, California, Monday, July 25, 2022.

Firefighters clear hot spots as they battle the Oak Fire in the Jerseydale community of Mariposa County, California, Monday, July 25, 2022.
(AP Photo/Noah Berger)

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At least 100 houses and structures have been destroyed.

Heavy smoke drifted more than 200 miles, reaching Lake Tahoe, parts of Nevada and the San Francisco Bay Area.

Officials are investigating the cause of the fire that broke out last Friday.

The Associated Press contributed to this report.