California's huge Dixie Fire exploded to "megafire" status late Thursday, forcing more mandatory evacuations in nearby communities, fire officials said Friday.
At more than 221 square miles in size, it's now the largest wildfire in California.
"The Dixie Fire is burning in a remote area with limited access, and extended travel times in steep terrain are hampering control efforts," Cal Fire said in a statement. The "fire will continue to rapidly expand, causing a need for the critical resources to control and manage the incident."
Shannon Prather, the incident commander for the Dixie Fire, said Thursday evening that "this fire is outpacing us at moments."
It is the second megafire in the state this year. A blaze becomes a megafire when it surpasses 100,000 acres, which is about 156 square miles. Days ago, the 105,000-acre Sugar Fire in Butte County garnered the designation, KTLA-TV said.
Another California fire, the Tamarack Fire near Lake Tahoe, had burned more than 78 square miles of national forest as of early Friday. The fire has destroyed at least 10 buildings.
Fire officials expected active or extreme fire behavior on Friday in the Tamarack Fire because of afternoon gusts and temperatures approaching 90 degrees.
Meanwhile, further north in Oregon, crews were making progress in the fight against the nation's largest fire, the Bootleg Fire, as weaker winds helped reduce the spread of flames there.
The fire, which has destroyed an area half the size of Rhode Island, was 40% contained after burning some 70 homes, mainly cabins, fire officials said.
At least 2,000 homes were ordered evacuated at some point during the fire and an additional 5,000 were threatened.
Nationally as of Friday morning, some 83 large fires and complexes were burning 1,366,587 acres, or roughly 2,135 square miles, the National Interagency Fire Center said.
"Almost 22,000 wildland firefighters and support personnel are assigned to incidents across the country," the NIFC said.
Smoke from the western fires continues to spread across the country Friday, leading to hazy skies and poor air quality in many areas. In northern Indiana, for example, the National Weather Service there warned that "high levels of fine particulates in the air due to smoke from western United States and southern Canada wildfires are expected to be in the 'orange' or 'unhealthy for sensitive groups' range."
The weather service added that "people with respiratory diseases such as asthma avoid prolonged outdoor exposure or exertion."
Growing research points to potential long-term health damage from breathing in microscopic particles of smoke, with millions of people potentially at risk far from where huge fires burn.
Contributing: The Associated Press
This article originally appeared on USA TODAY: Dixie Fire becomes megafire in California; Bootleg fire 40% contained