More than 1.3 million acres have burned thus far in the Golden State, according to the National Interagency Fire Center.
The center said 2.5 million acres have been scorched nationally this fire season.
Evacuation orders are in effect for residents near 17 large fires or complexes across the U.S. and more than 26,200 wildland firefighters and support personnel are working to snuff out the threatening flames.
The 126,182-acre Caldor Fire was just 11% contained on Thursday and has destroyed 637 structures since it was sparked on Aug. 14.
Officials said more than 2,500 firefighters were on the line and more resources were streaming in, including firefighting aircraft.
The Caldor Fire has since spread over the Sierra Nevada, dangerously close to Lake Tahoe, where skies were painted with thick, yellow-colored haze this week.
The air was so bad that schools in Reno, Nevada, – located approximately 60 miles from the fire – closed for two days and the Washoe County School District’s schools in Incline Village on the north shore of Lake Tahoe remained closed on Wednesday.
To the south, the South Coast Air Quality Management District issued an advisory through Thursday morning for large swaths of Los Angeles, Riverside and San Bernardino counties.
Microscopic particles in wildfire smoke – or PM2.5 – can lead to respiratory problems and other health issues, especially for people with chronic health conditions.
Government programs rely on data from around 950 permanent monitoring stations and mobile units around the country, though stations are notably concentrated around major cities on the West Coast and east of the Mississippi River.
The Caldor Fire wasn’t the only threat as a new wildfire in San Bernadino County forced the evacuation of 1,000 residents and quickly burned several hundred acres, including a dozen homes and structures.
The South Fire, which started on Wednesday, has already reached 500 acres, according to Cal Fire.
The 742,724-acre Dixie Fire – the largest single fire in state history – was 45% contained, burning about 65 miles to the north.
In addition, SFGate reported that the Grass Valley Police are ordering residents of the historic Gold Rush town to evacuate immediately due to the Bennett Fire, which also erupted on Wednesday..
Southern California’s smaller French Fire, near Lake Isabella, had also forced evacuation orders for 10 communities.
On Tuesday, President Joe Biden declared that a major disaster exists in California and ordered that federal aid be made available to local governments, agencies and fire victims in four northern counties.
Ninety-two fires are burning in 13 states, mainly in the West.
Anthony Scardina, deputy regional forester for the Forest Service, warned that large fires in northern California could burn into early December and that Southern California could expect to see fires in September that could last to the end of the year.