Hundreds of wildfires burning across Canada have sent thick smoke across north-eastern Canada and the eastern United States, with Toronto, New York and Washington DC recording some of the world's worst air quality on Saturday and health authorities urging people to limit time outdoors. Many blazes remain out of control, forcing evacuations and destroying property, including the near-total destruction of the Namaygoosisagagun First Nation community in northern Ontario, whose residents had to flee by boat. The smoke has also strained US-Canada relations, with President Trump threatening new tariffs over the "incalculable" cost of the smoke to the US, while poor air quality raised concerns ahead of the World Cup final in New Jersey.

According to the Canadian Interagency Forest Fire Centre, 955 wildfires are actively burning nationwide, with nearly 200 in Ontario, while more than a dozen fires span over 73,000 acres along the Minnesota border, prompting an "unprecedented" emergency declaration there. Six Ontario communities are under evacuation orders, though officials said fire activity was beginning to ease on Saturday, with air quality expected to improve. Experts attribute the surge to a "heat dome" trapping hot, dry air over the region since late June, which dried out vegetation and created conditions for fires and smoke to spread rapidly, alongside a risk of storms and strong winds fanning the blazes further.