Officials in Northern California are warning residents to stay indoors due to widespread hazardous air quality from the thick smoke produced by wildfires raging across the region.
The Placer County Public Health and the Placer County Air Pollution Control District issued an air quality advisory Thursday, forecasting hazardous smoke impacts and warning residents to stay indoors.
"Sad to say, the prediction is correct," Ann Hobbs, associate planner at the Placer County Air Pollution Control District, told CNN. Hobbs said officials had anticipated a change in the wind would bring poor air quality and smoke to residents living in the area.
"Avoid all unnecessary outdoor activity," Hobbs said, adding that the air quality is the worst the area has seen all year.
The thick smoke extended far beyond California, causing alarm in Utah. "Our dispatch centers are getting overwhelmed with calls about smoke; unfortunately, we are unable to change the jet stream," the Centerville Police Department said Friday in a tweet.
On Friday afternoon, air quality measurements from the EPA's AirNow website showed air quality readings for PM2.5, the fine particles produced by wildfire smoke, up to 921 in Chester, California, far beyond the 300 considered "hazardous." The air quality index in the town of Paradise was also hazardous at 602.
The Northern Sierra Air Quality Management District and the public health departments of Nevada, Plumas and Sierra counties issued a joint air quality health advisory due to the "prolonged and widespread smoke from numerous wildfires."
The widespread smoke and haze are expected to last at least through Saturday, according to the National Weather Service forecast office in Reno, Nevada.
"It was hard to breathe," Jake Edwards, a resident of Lake Almanor, California, told CNN. Edwards and his entire community were ordered to evacuate due to the Dixie Fire that has become the nation's largest so far this year.
"We are having a disaster over here," Edwards said.
The smoke from the wildfires is even affecting air quality further east. Denver, Colorado, had the worst air quality of any major city in the world for several hours Saturday, according to a world air quality ranking. Currently, Denver has the most polluted air in the United States.
The Swiss air quality technology company IQAir keeps track of the air quality index of 94 major world cities, where a higher number indicates lower air quality. It found that Denver's air was the most polluted on Saturday, with an AQI of 179, as measured by United States standards. It was followed closely by Johannesburg, South Africa, with a US AQI of 178.)
Concerns about air quality are one part of the impact from large wildfires in California and other Western states.
Two Northern California wildfires have destroyed dozens of homes, left people unaccounted for or injured and prompted additional evacuations Thursday -- all in less than 48 hours.
The Dixie Fire, now the largest active fire in the nation, has destroyed more than 100 homes and is expected to do more damage, according to Plumas County Sheriff Todd Johns.
Five people were unaccounted for as of Saturday, the Plumas County Sheriff's Office said, all of whom are residents of Greenville. Two have been reported safe, the sheriff's office said, but law enforcement has been unable to make official contact with them.
Five others who were previously unaccounted for have been recovered, the sheriff's office said. A total of 21 people who had been accounted for are now confirmed safe.
In 24 days, the Dixie Fire has consumed 446,273 acres -- an area 3.5 times the size of Lake Tahoe, making it the third-largest fire in California history.
The fire, which has burned an area equivalent to the size of New York's Central Park every 11 minutes for 24 hours, is 21% contained -- down from 35% Thursday. The massive blaze threatens roughly 14,000 structures.
Plumas National Forest Supervisor Chris Carlton described "truly frightening fire behavior" that has delivered even veteran firefighters into "uncharted territory."
"What I am telling folks at this time is if a plume of smoke is anywhere near your direction and you're still miles away from it, you need to prepare (to leave) even if you haven't heard that you are under a warning," Johns said.
The historic town of Greenville in Plumas County was nearly leveled to the ground. In the community's commercial center at Main Street and State Route 89, nearly every business appeared to have collapsed or been gutted, with flames still flickering in the debris up and down the sides of both streets, according to video recorded Wednesday by storm chaser Brandon Clement.
The fire's increased activity promoted officials to issue an additional evacuation order in Lassen County. The latest orders apply to areas north and east of Mountain Meadows Reservoir, according to the Lassen County Sheriff's Office.
Approximately 80 miles south, the River Fire raging in Nevada and Placer counties has obliterated at least 76 structures and at least 20 structures have been damaged, according to Cal Fire's Thursday night update. Damage assessment has not yet been finalized because inspectors are unable to access all affected areas as the fire grows.
Two residents and one firefighter have been injured in the fire, Cal Fire said. More than 800 personnel are fighting the blaze, which has burned 2,600 acres and is 48% contained, according to Cal Fire.
In Placer County, nearly 2,400 people are under evacuation, Placer County Sheriff's Office spokesman Nelson Resendes said Wednesday. In Nevada County, at least 4,200 residents are under an evacuation order or warning, said county Sheriff Shannan Moon.
Overall, 11 new large fires have been reported in the US, according to the National Interagency Fire Center. That brings the nationwide total to 107 large fires.