Smoke from wildfires burning across northern Ontario and the Prairies pushed Toronto's air quality to among the worst of any major city in the world on Monday, as Environment Canada kept air-quality and heat alerts in place across the Greater Toronto Area. Global trackers ranked the city near the top of the list of the most polluted urban centers as a haze settled over the skyline.
Environment Canada said the smoke was causing or expected to cause poor air quality and reduced visibility, and warned residents to limit time outdoors. The agency advised that people who must be outside wear a well-fitting respirator such as an N95 mask, and urged residents to keep windows and doors closed to protect indoor air.
Health officials flagged groups at higher risk from wildfire smoke, including people 65 and older, pregnant people, infants and young children, and those with existing illnesses or chronic conditions. They recommended such residents reschedule strenuous outdoor activities and watch for symptoms ranging from eye irritation to shortness of breath.
The smoke arrived alongside a spell of extreme heat and humidity, a combination that compounds the strain on vulnerable residents and on the power grid. Cooling centers and public health advisories were activated as the GTA contended with both hazards at once.
Toronto has weathered repeated bouts of wildfire smoke in recent summers as fires across northern Ontario and western provinces send plumes drifting south over densely populated southern Ontario. The recurring episodes have become a seasonal feature of life in the region, tied to a wildfire season that federal officials warn could be severe in 2026.
Forecasters said conditions would depend on shifting winds and the behavior of the fires upwind. Officials encouraged residents to monitor the Air Quality Health Index and local advisories, cautioning that smoke concentrations can change quickly from one day to the next.