By Editor — June 5, 2025

Toronto experienced a historic low in air quality today, briefly topping the charts as the most polluted city in the world, as wildfire smoke swept into the region from across Canada.

According to Environment Canada, smoke from out-of-control wildfires—particularly in northern Ontario and Western Canada—has drastically deteriorated the air across Toronto, the GTA, much of southern Ontario, and parts of five other provinces and one territory.

Air Quality Hits “High Risk” Levels

Earlier this afternoon, Toronto ranked second worst globally for air quality, before briefly taking the top spot at approximately 4:15 p.m., according to real-time data from Swiss air quality tracker IQAir.

On Friday, the city’s Air Quality Health Index (AQHI) is expected to reach a 7 out of 10, a level classified as “high risk” by Environment Canada.

“Only a few see the flames but millions smell the smoke,” said David Phillips, senior climatologist at Environment Canada. “What we’ve seen this week, of course, in Ontario is a lot of that smoke from fires has come south.”

Health Warnings and Safety Advisories

The federal agency issued a special air quality statement, urging residents to limit time outdoors, especially during the late morning and afternoon hours when smoke levels are expected to peak.

“As smoke levels increase, health risks increase,” the advisory warned. It recommended rescheduling outdoor sports, events, or physical activities, particularly for those with pre-existing respiratory conditions, pregnant individuals, seniors, and young children.

The smoke may cause mild symptoms such as irritation to the eyes, nose, or throat, headaches, and coughing. In more sensitive individuals, it could trigger wheezing, chest pain, or more severe respiratory issues.

A Summer Start Clouded by Smoke

Toronto residents, eager to enjoy summer after a late start, found themselves dodging more than rain clouds.

“It took so long for the summer-like weather to come,” Phillips said, “and when it came, not with blue skies… but some cruddy-smelling air that actually almost makes you wish spring-like weather was back.”

Looking ahead, air quality is expected to “bounce around” throughout the weekend, with lingering haze and smoke likely to persist until early next week.

Stay Informed:
For real-time updates on air quality in your area, visit Environment Canada’s website or check the IQAir app.