In photos: Firefighters battle 75 wildfires across the West on the first day of fall

Los Angeles County Fire Department firefighters worked into the night to tackle the massive BobCat Fire before the expected arrival of warmer and drier weather later in the week. The blaze has burned over 112,000 acres and was 17% contained late Tuesday.

The big picture: 75 large wildfires were burning in the U.S. Tuesday, the first day of fall, as cooler weather provided relief to firefighters and improved air quality across the West. The mega-fires have killed at least 36 people and charred more than 5 million acres in Oregon, Washington and California — where 26 people have died, over 7,1000 structures have been destroyed and more than 3.6 million acres have been razed.

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California

Firefighters near Wrightwood tackle the Bobcat Fire on Sept. 20. Photo by David McNew/Getty Images

Homes destroyed by the mostly contained Hennessey Fire in Napa, California, on Sept. 15. The fire has burned over 315,000 acres, razed 633 structures and killed five people. Photo: Justin Sullivan/Getty Images

A firefighter surveys the burned remains of Berry Creek School in California on Sept. 14. Photo: Josh Edelson/AFP/Getty Images

Cars drive along the Golden Gate Bridge under an orange smoke filled sky at midday in San Francisco, on Sept. 9, when air quality was among the worst in the world. Photo: Harold Postic/AFP via Getty Images

The #BobcatFire containment line, defined by yesterday's strategic burn to the north and west of the observatory, held overnight. This process may continue even further to the west today. pic.twitter.com/rMPKb7ZaYZ

— Mount Wilson Observatory (@MtWilsonObs) September 22, 2020

Oregon

Photo gallery: Assessing the damage after the Holiday Farm Fire. @registerguard #HolidayFarmFire #OregonWildfires2020 @ORDeptForestry #oregonwildfires #MckenzieStrong pic.twitter.com/qtgRPSsdUJ

— Chris Pietsch (@ChrisPietsch) September 23, 2020

A 12-year-old girl gets a free haircut from a hairdresser at the evacuation center at the Jackson County Fairgrounds in Central Point on Sept. 16. Photo: Paula Bronstein/AFP via Getty Images

Downtown Portland, Oregon, on Sept. 14. Air quality had improved significantly by Sept. 18. Photo: Robyn Beck /AFP/Getty Images Photo: Robyn Beck/AFP via Getty Images

Homeowners survey their property in a neighborhood destroyed by wildfire on in Talent on Sept. 13. Photo: David Ryder/Getty Images

A woman drops off donations for residents evacuated from the Riverside Fire at the Clackamas County Fairgrounds in Canby Sept. 13. Photo: Robyn Bec/AFP via Getty Images

Incident Commander for the Almeda Fire, Scott Magers, got to visit with K9 Officer Simon today. Officer Simon works as a...

Posted by Almeda and Obenchain Fire Information on Sunday, September 13, 2020

Washington

A seagull flies past cranes on Harbor Island as smoke from wildfires fills the air on Sept. 12 in Seattle. "Most of the wildfire smoke has left western WA," the PS Clean Air Agency tweeted Sept. 19. "Air quality throughout the Puget Sound has reached GOOD. We expect GOOD air quality for the rest of the weekend and well into next week." Photo: Lindsey Wasson/Getty Images

Smoke from wildfires obscure the Space Needle and the Seattle skyline on Sept. 12 in Seattle. Photo: Lindsey Wasson/Getty Images

Get to know your #firefighters - Introducing Aleshia DeLanoy who works w/Harrisburg Fire Dept. & as an anesthesia assistant at McKenzie-Willamette hospital. She says her favorite part of firefighting is helping those in need. Thanks so much for your incredible work, Aleshia! pic.twitter.com/FswQHCy1i3

— Forest Service NW (@ForestServiceNW) September 20, 2020

Montana

#callhanfire Containment increased to 40% yesterday as firefighters continued to extinguish heat along the fire’s southern...

Posted by U.S. Forest Service - Kootenai National Forest on Tuesday, September 22, 2020

A Flathead crew member "digging line around a spot fire on the Callahan Fire," according to the U.S. Forest Service on Sept. 18. Photo: Flathead Hotshots/U.S. Forest Service/FacebooK

Idaho

Burnouts along existing roads

🔥 #WoodheadFire Strong winds are expected to arrive tomorrow ahead of another cold front. In preparation of this weather small burnouts were conducted in Ditch Creek and in upper Olive Creek. Burnouts strategically remove grass, brush, and trees along the fireline under select, desirable conditions to lower fire intensity as the main fire approaches. This tactic is being used because it can take advantage of roadways and other selected fire breaks to be more efficient and effective than having firefighters construct line across the steep and rocky terrain. Latest updates → https://inciweb.nwcg.gov/incident/7163/ Most recent maps → https://inciweb.nwcg.gov/incident/maps/7163/

Posted by U.S. Forest Service - Payette National Forest on Tuesday, September 22, 2020

The Porphyry Fire is now 17,628 acres as fire progression was slowed thanks to rain and lower temperatures. Between a...

Posted by U.S. Forest Service - Payette National Forest on Monday, September 21, 2020

Part of Highway 21 between Grandjean and 10 miles outside of Stanley, is closed due to a wildfire in Salmon-Challis National Forest. Photo: U.S. Forest Service/Facebook

The Trap Fire was reported on the Sawtooth National Forest on Sept. 14 and is "burning on both sides of Highway 21," the U.S. Forest Service notes. Photo: U.S. Forest Service/Facebook

Go deeper: Portland has world's worst air quality as West Coast fires raze 5M acres

Editor's note: This article has been updated with more details and images from the fires.