As one of the largest wildfires in California history, the Park Fire in Northern California, continued to rage Monday, another blaze in the Western U.S. ignited in Northern Colorado prompting evacuations.
The Park Fire in Northern California was racing across four counties Monday and threatening more than 4,200 structures as thousands of firefighters struggled to increase containment lines, officials said.
In Colorado, the Alexander Mountain Fire ignited near Roosevelt National Park in Larimer County, north of Boulder. The fire was estimated to have spread to 365 acres as of late Monday afternoon based on the latest infrared flight to map the perimeter, according to the U.S. Forest Service. The Larimer County Sheriff's Office had previously said the fire was at 800 acres before later revising the size to 365 acres.
The Larimer County Sheriff's Office ordered residents in the Alexander Mountain and Palisade Mountain areas to "evacuate immediately" as local fire crews and firefighting aircraft raced to battle the blaze.
Meanwhile, the Park Fire, which California authorities said was deliberately ignited last Wednesday afternoon, had spread to 373,357 acres by Monday afternoon, or more than 583 square miles, through Butte, Plumas, Shasta and Tehama counties, according to the California Department of Forestry and Fire Protection (CAL FIRE). Containment on the fire remains at 12%, officials said.
"This proactive approach aims to safeguard the communities and ecological and cultural resources that may be at risk from the fire," CAL FIRE said in its statement.
The high temperature on Monday in the fire zone was forecast to be 94 degrees, according to the National Weather Service. By the end of this week, temperatures are forecast to spike back into the 100s, according to the weather service.
California Gov. Gavin Newsom declared a state of emergency for Butte and Tehama counties due to the Park Fire, as well as Plumas County, where the Gold Complex Fire, which started on July 22, has burned more than 3,000 acres and was 50% contained on Monday.
Ronnie Dean Stout II, 42, was arrested on suspicion of arson in the Park Fire after he allegedly pushed a burning car into a gully in Bidwell Park, near Chico, according to Butte County District Attorney Mike Ramsey.
Stout was formally charged with felony arson, with an enhancement of special circumstances due to prior convictions, during his arraignment on Monday and remains held without bail, court records show. His arraignment has been continued until Thursday. Attorney information was not immediately available.
"I don't know if I'd say I'm angry, but frustration and unnecessary, yes," Chico-area rancher John Russell told ABC News of learning the fire was allegedly deliberately set.
Russell said the fire burned up to this property line but was stopped by firefighters who cut a fire line around his land with a bulldozer to save his barn and cattle.
"I know I'm being recorded, so I won't say obviously, I'll put it tactfully... Our cattle survived. We can go on. We can fix the rest. But truly, the real damage and sadness and anger would come from the people who have lost everything," Russell said.
There are more than 4,800 personnel, 33 helicopters and 434 fire engines assigned just to the Park Fire, officials said.
"Numerous firefighting air tankers from throughout the state are flying fire suppression missions as conditions allow," according to CAL FIRE.
A fire burning near the Sequoia National Park, the 2024 SQF Lightning Complex Fire in Tulare and Kern counties in Central California, is the second-largest blaze burning in the state, having consumed 85,583 acres since starting on July 13, according to CAL FIRE. The blaze was 33% contained on Monday.
The heavy smoke from fires in Northern California and Oregon is spreading across several states, including Nevada, Idaho, Utah, Wyoming and Montana. By Monday afternoon, some of the heavy smoke is expected to reach as far as the Dakotas and Nebraska.
This fire season in California began in earnest in early July and hasn't slowed down since, officials said. So far this year, 4,574 fires have erupted in the state and have burned a combined 726,667 acres, an increase of 2,744% from this time last year, according to CAL FIRE.
ABC News' Mola Lenghi and Jaclyn Lee contributed to this report.
Editor's note: This story has been updated.