Extreme, prolonged heat wave expected to cover much of southern Ontario

Environment Canada has issued an orange alert as an intense and prolonged heat wave is expected to blanket much of southern Ontario, including Toronto, starting today.

The weather agency says the heat wave will continue through Friday and possibly into the weekend before temperatures drop slightly early next week.

It says maximum temperatures in Toronto are expected to reach 33 C with a humidex of 42 C today with a 40 per cent chance of showers and a risk of thunderstorm.

It says temperatures will hover between highs of 35 C and lows of 23 C for the rest of the week.

Environment Canada says hot and humid air can also lead to deteriorating air quality.

The agency is urging Ontarians to limit direct exposure to the sun and heat, and check on family members and neighbours who are at high risk of heat illness or living alone.

This report by The Canadian Press was first published June 30, 2026.

The Canadian Press