Step outside and you'll probably smell it—smoke has been a major issue across much of Eastern Canada this weekend. Montreal and Toronto made the list for the top-five major global cities with the worst air quality on Sunday. The cities ranked fourth and fifth, respectively, with air quality values in the “unhealthy for sensitive groups” range.

Hazy skies from wildfire smoke from Canada, which may become more concentrated with visibility potentially dropping to 3-5 miles at times, and air quality dropping to the unhealthy category.