Wildfire smoke from Canada causes air quality alerts in Midwest cities.

Wildfires in Canada have caused heavy smoke to drift south across North America, prompting air quality warnings in parts of Canada and the US Midwest. Cities including Chicago and Milwaukee, as well as parts of Michigan and Ontario, registered air quality index levels in the 200s on a 500-point scale, considered "very unhealthy". Health authorities have advised vulnerable groups to limit outdoor activities. This year's wildfire season is the worst on record in Canada, with nearly 500 fires still burning and 7.7m hectares already set ablaze, releasing a record 160m tonnes of carbon into the atmosphere.