Air quality has taken a serious hit across the United States as a two-fold 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.

Researchers found that wildfire smoke can raise ozone to dangerous levels, posing hidden health risks even in remote areas.

The National Weather Service says Canadian wildfire smoke will return to Michigan Monday. Residents in northern Michigan should take precautions.