(CNN) - The deadly wildfires are not only destroying homes and burning everything in their path -- but they're also causing poor air quality.
On Tuesday, a thick haze blanketed parts of the Northwest, including Seattle, as fires across the border in Canada burned. Things were looking a little better Wednesday, as cleaner air began pushing onshore, according to the National Weather Service in Seattle, which said the state had the worst air quality in the country.
The smoke that is blanketing Washington, Oregon and California is smoke coming from the wildfires burning in British Columbia, according to the National Weather Service Seattle.
Air quality advisories were in effect for portions of Washington and Oregon, according to the weather service.
The air quality was considered unhealthy in western parts of Washington.
The unhealthy level on the Air Quality Index means that everyone could experience health effects, with possibly more serious health issues for children, seniors and people with medical conditions. Wildfire smoke can include particles from burning vegetation and building materials mixed with gases.
The Washington State Department of Natural Resources said Wednesday things had improved at bit.
"Most monitors in Western Washington are still in the unhealthy range due to lingering smoke, but more clearing is expected through tonight and tomorrow. It may be short-lived, but we expect at least a couple days of cleaner air coming up," a multiagency update said.
Wildfire smoke was visible from space as it covered parts of Washington on Tuesday.
Glacier National Park affected by fire
Also out West, firefighters are battling a lightning-caused fire at Glacier National Park that prompted evacuations and destroyed several structures.
The Howe Ridge Fire ignited Saturday at the national park in Montana, spreading rapidly over the weekend. It has also sent a widespread haze of smoke in the area.
California has 11 large fires, BC has nearly 600 wildfires
As 11 large fires raged in California, there were hotspots of unhealthy air quality in certain parts of the state -- especially near the wildfires. On Tuesday, most parts of the state were considered moderate in terms of air quality, according to the EPA's AirNow site.
Also on Tuesday, Yosemite Valley, which had been closed for nearly three weeks due to a fire, reopened to visitors.
But Yosemite National Park's website warned of poor air quality and visibility at times due to the Ferguson Fire.
In British Columbia, more than 10,000 homes across the province are on alert to evacuate due to the nearly 600 wildfires burning, BC Wildfire Service spokesman Kevin Skrepnek said.
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