As Canada grapples with one of its worst wildfire seasons on record, smoke from the blazes have prompted air quality alerts across the U.S.

A thin veil of smoke from wildfires burning in Canada is worsening air quality and putting a lid on temperatures in the D.C. area. The smoke, which has resulted in some of the world’s worst air quality in the Upper Midwest and Northeast, is only wafting through the Mid-Atlantic in limited quantities, but it’s enough to have a small impact.

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