Smoke from ongoing wildfires across Canada continued to drift into parts of the United States on Wednesday, causing hazy skies and triggering air quality alerts in multiple states across the upper Midwest and Northeast.

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.

Hundreds of wildfires still burning in Canada are expected to undermine air quality across the Upper Midwest and Northeast into Tuesday.