Environment Canada is warning of poor air quality and extreme heat in Toronto on Monday as southern Ontario braces for a week filled with hot and humid weather.

In Canada, the Air Quality Health Index (AQHI) is a scale developed to help people understand what the current air quality means for your health. It is an initiative among Environment Canada, Health Canada and the provincial governments.

Environment Canada urges residents to limit their time outdoors. But even when inside, most buildings can only reduce airborne pollutants by half.

Environment Canada warned on Thursday that poor air quality in the Toronto area would likely last into Friday. “Wildfire smoke can be harmful to everyone’s health even at low concentrations ...