How long will wildfire smoke impact southern Ontario?

Smoke from wildfires in northern Ontario has moved into southern Ontario, leading to very poor air quality.

Toronto ranked worst in the world for air quality Wednesday morning, ahead of Kinshasa in the Democratic Republic of the Congo and Dehli, India.

The sky has turned orange and there is a strong smell of smoke outside.

Environment Canada has issued air quality warnings for a large swath of the province.

READ MORE: Smoke warning in effect across Toronto and southern Ontario

So how long is the smoke expected to impact southern Ontario?

Poor conditions are expected throughout the day on Wednesday.

Environment Canada’s wildfire smoke fine particulate matter model shows much of the region blanketed in smoke well into the evening.

That continues through the overnight hours into Thursday.

According to the forecast model, conditions may get slightly better mid-afternoon Thursday for areas including the Greater Toronto Area, to the north and east.

By 8 p.m. Thursday, however, thick smoke will have moved back in.

That continues through the overnight into early Friday morning.

By 7 a.m. Friday, the model shows smoke clearing from the Greater Toronto Area and areas north of it.

Thick smoke continues in extreme southwestern Ontario, however, and that lingers until at least 8 p.m. Friday, which is the furthest point the model forecasts.

That aligns with the reading of the air quality warnings issued by Environment Canada.

Forecasters said that conditions in areas including the GTA “may improve Friday morning.”

The warning for extreme southwestern areas, including Windsor, says “poor air quality may persist into Friday.”

“During heavy smoke conditions, everyone’s health is at risk regardless of their age or health status,” the orange alerts say.

“Limit time outdoors. Reschedule or cancel outdoor sports, activities and events.”

A yellow heat warning is also in effect for southern Ontario, with highs of 29 C to 33 C possible on Wednesday and humidex values of 38 to 42.

However, forecasters said the smoke may limit the heat.

“Widespread wildfire smoke may limit daytime heating, leading to cooler temperatures than expected.”

Eerie scenes across #Toronto as dense wildfire smoke settles in#OnWX #ONStorm pic.twitter.com/2BBW4A79Ha

— WxOntario (@WxOntario1) July 15, 2026

That’s not cloud cover across SW #Ontario…that’s dense wildfire smoke from the fires across NW Ont

Wildfire smoke drifts SE through the afternoon#OnWX #ONStorm pic.twitter.com/wLKMBHlJiP

— WxOntario (@WxOntario1) July 15, 2026