Wildfire smoke from Canada is impacting states in the northern tier of the U.S. this week.
Offices of the National Weather Service in cities across the country tweeted to warn residents of impacts, including in Seattle, Pittsburgh, the Twin Cities, Bismarck, Topeka, Pendleton, Boulder, Billings, Chicago, Little Rock and elsewhere.
In Boise, Idaho, the office said Thursday that "hazy skies" were in its future.
"Wildfire smoke from Canada will start making its way into eastern Oregon and Southwest Idaho within the next several days," it warned. The Pocatello office said Idahoans should not be surprised to smell the smoke at times.
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"The smokey, hazy skies are from wildfires in western Canada," the Cleveland office said. "That smoke is drifting through the higher levels of the atmosphere. Current air quality is good to moderate across northern Ohio and Northwest Pennsylvania."
In Des Moines, Iowa, the agency warned about smoky weather conditions leading to "reduced visibilities," lingering into Friday morning.
In Duluth, Minnesota, sinking air with rain caused the smoke there to reach the surface and an Air Quality Alert was in effect for much of the northeastern region of the state.
Fox Weather reported that such alerts were also in place in Washington state and Montana, noting that visibility may drop as low as a quarter mile in areas of Montana, Minnesota and the Dakotas.
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The offices also shared images on Twitter of red-tinged suns and skies shrouded in smoke.
While the more than 90 fires blaze in Canada's Alberta province, the Albany, New York, office said there could be some smoke aloft, and the National Weather Service in Boston said to "say goodby to those beautiful blue skies."
Fires in western Canada have forced the evaluations of tens of thousands.
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A national situation report from the Government of Canada says there are currently more than 30 uncontrolled wildfires. The province has declared a state of emergency in response to the fires.
Wildfire smoke can have adverse health impacts, hurting a person's eyes, irritating the respiratory system and worsening chronic heart and lung diseases, according to the Centers for Disease Control and Prevention.