Six Flags Great America and Hurricane Harbor Chicago in Gurnee, Illinois, were forced to close due to smoke from Canada's wildfires, causing unhealthy air conditions across the Chicago area. The park is expected to reopen Saturday, pending improved conditions. An air quality alert remains in effect across the area until Saturday night. The Canadian government had 859 active wildfires, including 113 classified as out of control. The smoke has affected large parts of the US, including the Great Lakes, Northeast and Mid-Atlantic, exposing over 100 million people to unhealthy air. President Trump threatened new tariffs on Canada over the wildfire smoke, accusing the country of failing to manage its forests.