Air quality has taken a serious hit across the United States as a twofold blow of wildfires in the West and in Canada have sent smoke pouring across large sections of the country — a problem that’s set to linger for days.

Millions in the United States are facing another day of hazy skies fueled by hundreds of smoky wildfires burning across North America, impacting air quality in parts of the U.S. and raising health concerns.

Smoke from Canadian wildfires is causing air quality concerns for millions of Americans in the Midwest and Northeast. Air quality alerts were in effect Tuesday in several states, including Wisconsin,