Toronto's air quality remains severely compromised due to lingering smoke from wildfires in the Prairies. On Thursday morning, IQAir, a Swiss air quality technology company, reported that Toronto had the fourth worst air quality among major cities worldwide. By midday, the city improved to 10th place, but it still faced significant pollution levels. Kinshasa, the capital of the Democratic Republic of Congo, topped the list for the worst air quality.

The air quality in Toronto was initially classified as "unhealthy for sensitive groups" but later downgraded to "moderate" by early afternoon. Residents have been dealing with haze throughout the week, as the air is filled with PM2.5 particles. These tiny pollutants, which include smoke, soot, mold, bacteria, and animal dander, are particularly dangerous because they are less than 2.5 micrometers in diameter and can enter the bloodstream when inhaled.

On Thursday morning, the concentration of PM2.5 in Toronto exceeded the World Health Organization's guidelines by more than seven and a half times. Areas such as Greenwood, Danforth, The Beaches, and the Annex are experiencing the worst air quality, according to IQAir's monitoring stations.

Health officials are advising individuals with heart and lung conditions to consider postponing outdoor activities. Environment Canada has also recommended that the general public be vigilant for symptoms like coughing or sore throat. The agency predicts that air quality will remain at "moderate risk" levels until at least Friday night.

Other municipalities in Ontario, including Oakville, Kitchener, Burlington, and Uxbridge, are also facing poor air quality due to wildfire smoke. These areas are expected to see improvements in air conditions throughout Thursday.

The smoke may cause mild symptoms such as irritation of the eyes, nose, and throat, as well as headaches or a mild cough. More severe symptoms, including wheezing, chest pain, and intense coughing, indicate a need to stay indoors. Anyone experiencing a medical emergency should seek immediate assistance.

To minimize smoke exposure indoors, residents are advised to keep windows and doors closed and consider using air filters and ventilation systems. Wearing a well-fitting respirator mask, such as a NIOSH-certified N95, can also help reduce exposure to fine particles in outdoor smoke.

In terms of weather, Toronto is expected to experience a high of 27 degrees Celsius, feeling like 33 with humidity. The UV index is rated as "very high" at 8, with afternoon winds reaching 20 kilometers per hour. Nighttime temperatures will drop to around 20 degrees Celsius. The forecast for Friday indicates mostly sunny conditions with a high of 30 degrees Celsius, while the weekend will see temperatures reaching up to 32 degrees Celsius.