Little Improvement Expected in Ontario’s Air Quality Heading Into Weekend as Smoke Affects Much of Province

Buildings are seen from the observation deck of the CN Tower as smoke from forest fires in northwestern Ontario blankets Toronto, July 16, 2026. The Canadian Press/Cole Burston

Wildfire smoke continues to cause poor air quality across much of Ontario today, with minimal improvement expected heading into the weekend.

Revised forecasts indicate that several regions may not experience the clear skies originally predicted as smoke from ongoing wildfires in the northwest is being pushed south by shifting winds.

There were slight improvements in southern Ontario air quality overnight but conditions worsened by morning.

Environment Canada categorized the air quality health index (AQHI) as high to very high risk throughout large swaths of the province as of 9 a.m. Several of the cities in southern and southwestern Ontario are being assigned a rating of 10+, the highest risk level on the index.

The change in wind patterns has provided some respite to eastern Ontario, as air quality measurements have fallen below a level seven—the threshold at which severe air quality alerts are issued.

Here’s a look at what Ontarians can expect today and throughout the weekend.

Southwestern Ontario

Persistent poor air quality is expected to continue in Southwestern Ontario until the weekend, especially in Windsor, Sarnia, London, and the surrounding regions.

All three cities had an air quality rating of 10+ throughout the morning and the widespread smoke is expected to linger over the areas throughout the rest of the day into the evening hours.

Local smoke is expected in the morning and early afternoon on July 18 but rain throughout the day is expected to improve the air quality to a more moderate yellow rating by evening.

Toronto

Air quality readings in Toronto have improved vastly since earlier this week when the city placed first on the world’s most polluted air list.

Air quality measurements in the city showed minor variations, with the eastern area categorized as low risk, while downtown Toronto and the northern region were assessed as moderate. Conversely, the western part of the city continues to be at high risk, leading to an orange air quality alert for Toronto overall.

Environment Canada is forecasting that smoke will be localized in the morning, but it will become widespread by the afternoon and linger into the evening. Torontonians can also expect some localized smoke on July 18 but clearer skies the following day.

Southern Ontario

While Toronto has experienced an improvement in air quality, many of the neighbouring cities, including Hamilton, have not.

Hamilton continues to have a “very high risk” air quality rating of 10+ as do nearby Burlington, Brantford, and Guelph. Kitchener 100 kilometres to the west of Toronto has the same 10+ rating.

In the Greater Toronto Area (GTA), Milton was classified as a “high risk” with a score of 9, whereas Brampton and Oakville were positioned at the lower spectrum of the high risk category, scoring 7. Mississauga and Newmarket were assigned a “moderate” rating of 6.

Environment Canada is forecasting widespread smoke for most of Southern Ontario through nightfall and localized smoke on July 18.

Northern Ontario

The air quality in Thunder Bay continues to be dangerous due to the northwestern city’s proximity to the wildfires. Environment Canada is predicting widespread smoke to prevalent in the city through at least July 18.

The air quality has improved in Sault Ste. Marie today after heavy smoke in the atmosphere earlier in the week. It held a moderate rating of 5 throughout the morning; however, the orange air quality warning remains in effect as the environmental agency forecasts extensive smoke later today and continuing through July 18.

To the east, Sudbury and North Bay were assessed as low risk during the morning of July 17; however, Environment Canada predicts local smoke to develop late in the afternoon and persist throughout the next day.

Eastern Ontario

Cities east of Toronto are enjoying  improved air quality today due to a shift in air currents.

The smokey skies over Peterborough and Belleville, and Kingston have cleared and all three cities were rated as low risk on July 17.

Looking ahead, winds could carry smoke into eastern Ontario by the evening and the Ottawa Valley on July 18, potentially elevating air quality levels to moderate or high.