Poor air quality has returned in large portions of the country and is expected to linger through the early portion of the week, according to the National Weather Service.
Smoke from Canadian wildfires is projected to impact Americans through Tuesday as winds funnel the haze into the continental United States, the weather service said.
Air quality alerts were issued for areas including the northern high Plains, the Midwest, Great Lakes, central Tennessee and North Carolina, and the Northeast.
According to the weather service, higher concentrations of smoke will result in unhealthy air quality for sensitive groups.
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“Smoke concentrations should diminish over parts of the Heartland on Tuesday, but may still cause poor air quality along the East Coast,” the weather service said.
As of Monday morning, Chicago and Detroit have the worst air quality conditions among American cities, according to IQ Air’s live ranking of major world cities, which ranks them 4th and 13th, respectively.
According to the Canadian Interagency Forest Fire Centre, there are currently 580 blazes “out on control” and over 880 active fires.
Health experts advise Americans under air quality advisories to stay indoors with air conditioning or to wear N95 masks outside.