Seven states are under alert for poor air quality due to fires in the United States.

California burns: four fires are still active 1:07

(CNN) -

Seven western states are under air quality alert due to raging wildfires, which have forced thousands of people to evacuate and destroyed hundreds of homes.

The 92 major wildfires currently burning in the United States have burned more than 1,011,714 hectares according to the National Interagency Fire Center, and their smoke has put thousands of people on alerts for poor air quality.

Areas of California, Nevada, Oregon, Colorado, Wyoming, Idaho and Montana were under air quality alerts on Wednesday, according to the National Weather Service (NWS).

Thick smoke blanketed Lake Tahoe resort communities this week as the Caldor Fire, burning east of Sacramento, California, continued to grow.

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And in Reno, Nevada, residents were advised to stay indoors due to historic poor air quality.

Nevada's Washoe County, where Reno is located, had the worst air quality on two consecutive days, county health officials reported Tuesday.

The average air quality index for fine particulate matter reached 251 on Sunday, which is considered "very unhealthy," and on Monday, the index number jumped to 291, the Washoe County Health District said.

Smoke from the fires is expected to continue to be a problem for the area, CNN meteorologist Michael Guy said, as it specifically persists in parts of the Intermountain West, southern Oregon and the Great Basin, which includes parts of western Nevada. .

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"For the rest of this week, it looks like smoke will continue to be a problem for portions of the west," Guy said.

"Another storm system will approach the Pacific Northwest during the day, allowing the winds to change and some areas to clear. However, smoke remains a problem throughout the region as the overall weather pattern does not seems to change until the end of this week. "

California burns: four fires are still active 1:07

For Oregonians, the NWS advises staying indoors with windows closed when smoke levels are high.

"The wildfires burning in the region, combined with forecast conditions, will cause air quality levels to fluctuate and may be at unhealthy levels," the NWS wrote in its Oregon alert.

One of the most worrisome fires for California firefighters is the Caldor, in El Dorado County.

The 11-day fire has devastated 51,064 hectares and was 11% contained as of Wednesday morning, according to Cal Fire.

The massive fire has so far destroyed 461 homes and 11 businesses, according to Cal Fire.

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California fire is the top priority for the nation's firefighters

Authorities previously called the behavior of the Caldor fire "unprecedented", and are now concerned about how it will move in the coming days.

The fire threatens to move into the populated region of the Lake Tahoe Basin, making it the nation's top firefighting priority, Chief Thom Porter of the Department of Forestry and Fire Prevention said Monday. Of California.

"Personally, I don't think the fire is going to enter the basin proper," Porter said of Lake Tahoe, "but I could be wrong about that."

Time has come by and Mother Nature has taken it upon herself to bring fires like the Dixie to places I never thought were possible. "

The Emerald Bay of Lake Tahoe is shrouded in smoke from the Caldor Fire, near South Lake Tahoe, California, on August 24, 2021.

President Joe Biden on Tuesday approved California Governor Gavin Newsom's request for a presidential disaster declaration, which allows for additional federal resources to help support emergency firefighting efforts in the state, the governor's office said. in a press release.

Federal aid will go to communities in Lassen, Nevada, Placer and Plumas counties affected by the Dixie and River fires, the governor's office said.

Aid can support medical services, housing assistance and legal services, as well as response and recovery costs.

Dixie fire devastates 630 California homes 1:01

As of Tuesday night, a total of 37,282 people have been evacuated across the state due to the wildfires, Newsom's office noted.

California's wildfire season this year has been devastating, burning more than 655,590 hectares so far, and that number will only increase as the fires continue to grow.

The Dixie Fire, the second-largest fire in state history, burning for more than a month, has grown so large that its perimeter spans more than 1,295 square kilometers.

The fire increased to 297,469 hectares and is 45% contained, according to Cal Fire.

Authorities have warned that people must be prepared to evacuate quickly if necessary.

- Alexandra Meeks, Andy Rose and Cheri Mossburg contributed to this report.

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