Wildfire smoke from Canada is expected to move over the U.S., impacting air quality for millions of people on Friday and this weekend.  Maps and satellite imagery show the large-scale impact of the blazes.

According to forecasters at AccuWeather, cities where smoke is expected to become thick enough to be noticeable include Fargo, North Dakota; Minneapolis and Duluth, Minnesota; Green Bay and Milwaukee; and Chicago, Illinois. Additionally, high-altitude wildfire smoke may be visible as far southeast as Detroit and Indianapolis.

Smoke from Canadian wildfires is working its way into the northern U.S. this week, prompting warnings from health officials that air quality may become briefly unsafe.