Canada wildfire smoke triggers air quality warnings across Ontario, Minnesota

Smoke from wildfires in northwestern Ontario drove air quality warnings across Ontario and into Minnesota, where forecasters said heavy haze would spread through Thursday and Friday. The plume darkened skies over Toronto and drifted into the northeastern United States as officials urged residents to cut back on time outside.

Environment and Climate Change Canada said the smoke was causing very poor air quality and reduced visibility in parts of Ontario. The province’s Air Quality Health Index reached very high-risk levels in several communities on July 15, with readings of 10-plus in Kitchener, London, Parry Sound, Port Stanley, Sarnia and Grand Bend. Officials said those conditions could leave even healthy people feeling the effects, including eye, nose and throat irritation, headaches and coughing.

In Minnesota, the Pollution Control Agency said heavy wildfire smoke was expected to affect central and northern Minnesota before spreading into northwest Minnesota through Thursday and Friday. The state’s air quality alert remained in effect through Friday morning, and health guidance warned that everyone’s health was at risk during heavy smoke conditions, regardless of age or baseline health. Visibility was also expected to drop as the haze moved across the region.

The smoke episode unfolded against a much larger national fire season. The Canadian Interagency Forest Fire Centre said 838 wildfires were actively burning across Canada, underscoring the scale of the emergency stretching from northwestern Ontario to the Great Lakes and beyond. Canada’s recent fire seasons have already been extreme, with more than five million hectares burned in 2024 and 16 million hectares burned in 2023.

Environment and Climate Change Canada’s smoke dispersion forecasts and AQHI maps tracked how the plume could move over the next 72 hours, a reminder that air quality can change quickly across Ontario and into the northern United States. For communities under the haze, the warning was immediate: conditions were not only visible in the sky, they were measurable in the air residents breathed.