Environment Canada has issued special air quality advisories for large swaths of Ontario and Quebec, warning of high levels of pollution from wildfires burning across both provinces.
Ottawa, Belleville and Kingston registered some of the worst air pollution levels in the country, maxing out the air quality index at very high risk.
Air quality index levels were forecasted to peak at high risk in many other Ontario cities, from Windsor through to Toronto and north to Sudbury.
Toronto District School Board says all strenuous outdoor activities will be rescheduled, or moved indoors when possible, while school boards in York Region say they will hold recess inside.
As of Tuesday, there were more than 200 forest fires burning across Quebec and northern Ontario.