Canadian wildfires send hazardous smoke across US states

Smoke from more than 800 wildfires in Canada has spread across at least 20 US states this week. The fires are burning in central Canada and Ontario, and wind has carried thick smoke south across the Great Lakes. Air quality has reached dangerous levels in parts of Michigan, Wisconsin, and Minnesota. Officials there have told residents to stay indoors. Some areas recorded an air quality index of 500, which is the highest hazardous level. Ratings of "very unhealthy" covered parts of Illinois, Ohio, and other nearby states. Millions of people face health risks, and doctors have warned vulnerable groups to avoid going outside. Smoke was expected to reach New York City and Boston by mid-afternoon. By Monday, a change in wind direction should push the smoke toward Quebec.