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.

Health officials from Minnesota to Maine have issued alerts warning of poor air quality from wildfires burning in Canada. People are advised to limit outdoor exposure.