Extreme heat, bone-dry vegetation and human misconduct prompting intense wildfire season

It's only August, but already the U.S. wildfire season has burned more than 4.4 million acres, up a staggering 278% from last year, the National Interagency Fire Center reported Thursday.

Fueled by record high temperatures, including prolonged heat waves that have left many parts of the West with bone-dry vegetation, firefighters were battling 93 large active wildfires on Thursday in 13 states, including 28 fires that have prompted evacuations, according to the fire center.

With precipitation in the West below normal for July, some of the largest fires in U.S. history have ignited, especially in California and Oregon where a combined 44 fires were burning on Thursday, according to the fire center.

"Warming temperatures, drier conditions, and shifts in precipitation are contributing to an increase in the frequency of large wildfires and acres of land burned in the U.S. each year," according to the National Oceanic and Atmospheric Administration.

A prime example is the Park Fire in Northern California, which officials said was deliberately set on July 24 and rapidly spread through dry vegetation to become the largest active fire in the nation and as of Friday was the fourth-largest wildland blaze in California history.

"Year-to-date annual acres burned for the U.S. is above the 10-year average at 123% of normal," according to a statement from the National Interagency Fire Center.

The fire center added, "In comparison to the outlook issued a month ago, larger areas of the West are expected to experience above normal significant fire potential in August and September."

And just because most of the wildfire activity is happening in the West, that doesn't mean the rest of the country is immune from the effects.

"Western wildfires account for about half of the smoke that the rest of the contiguous U.S. experiences each year," according to Climate Central, an independent group of scientists that researches climate change.

The average number of heat waves major U.S. cities experience each year has doubled since the 1980s, according to the federal government’s Fifth National Climate Assessment. In the United States, summer minimum nighttime temperatures are warming nearly twice as fast as summer maximum daytime temperatures, according to Climate Central.

No state has experienced a worse wildfire season than California. The number of acres consumed by flames in the Golden State as of Thursday is 768,137, an increase of 2,905% from 2023, according to the California Department of Forestry and Fire Protection (Cal Fire). The 4,696 wildfires that have erupted in the state this year have destroyed more than 700 structures, including homes and commercial property, according to Cal Fire.

Here are some of the largest fires burning in the West:

The Park Fire in California

Firefighters battling the Park Fire in Northern California, the largest active fire in the nation, made significant progress in the past three days, increasing containment lines on the blaze to 24% as of Friday, according to Cal Fire.

The Park Fire, which officials said was deliberately started on July 24 and spread through Butte, Plumas, Shasta and Tehama counties in Northern California, has grown to 397,629 acres. The blaze leapfrogged Thursday over the 2020 SCU Lighting Complex Fire -- which tore through Santa Clara, Alameda, Contra Costa, San Joaquin, Merced, and Stanislaus counties -- to become the fourth-largest wildfire in state history, officials said.

The Park Fire has destroyed at least 540 structures and damaged another 50, according to Cal Fire. No fatalities or injuries have been reported.

More than 3,800 people have been evacuated due to the Park Fire, Cal Fire said.

Ronnie Dean Stout II, 42, of Chico, has been accused of starting the blaze and was arrested on a charge of felony arson with an enhancement of special circumstances. On Thursday, Stout made his second court appearance this week. His arraignment was continued to a later date to allow his public defender to review the case reports and determine a plea, according to ABC affiliate station KRCR in Redding, California.

Stout, who remains in jail without bail, was allegedly spotted just before 3 p.m. PT on July 24 pushing a burning car down a gully called "Alligator Hole" in Bidwell Park, near Chico, sparking the Park Fire, prosecutors said.

The Nixon Fire in Southern California

California firefighters were also confronting the Nixon Fire that Monday off Richard Nixon Boulevard in Riverside County, northeast of the town of Aguanga, according to Cal Fire.

As of Friday, the Nixon Fire had grown to 5,222 acres and was 21% contained, according to Cal Fire.

At least four structures in the fire zone were destroyed, according to Cal Fire.

The Alexander Mountain Fire in Colorado

Colorado firefighters were also trying to get the upper hand on the Alexander Mountain Fire, which was first reported Monday morning, according to the Larimer County Sheriff's Office. The fire burning in a remote mountainous area near Roosevelt National Park grew to 9,053 acres by Friday morning, according to the U.S. Forest Service.

The fire was 5% contained, according to the Forest Service.

Stone Canyon Fire in Colorado

The Stone Canyon Fire, west of Rabbit Mountain and the town of Lyons, had burned 1,553 acres as of Thursday night, according to the Boulder Office of Disaster Management.

The blaze was 30% contained, officials said.

The remains of a person were recovered from a home in the area of the Stone Canyon Fire on Wednesday, according to Boulder County Sheriff Curtis Johnson. But Johnson released few details on the circumstances of the death.

Quarry Fire in Colorado

The Quarry Fire, burning southwest of Denver in Jefferson County, is being investigated as arson after fire investigators found suspicious evidence on Thursday, the Jefferson County Sheriff's Office told ABC News.

"We preliminarily believe that this fire is human-caused in some manner," Kevin Bost, chief of investigations with the Jefferson County Sheriff's Office, said during a press briefing Friday morning.

No additional details were released amid the investigation.

The wildfire has burned more than 450 acres since originating on Deer Creek Tuesday night, prompting evacuations, authorities said.