Punishing temperatures return to Ontario and Quebec during record-breaking heat wave

A man cools sits in a picnic table in the waters of the Rideau River in Ottawa on Monday, June 23, 2025. THE CANADIAN PRESS/Adrian Wyld

A heat wave is set to deliver another day of punishing heat and humidity to parts of Ontario and Quebec.

Heat warnings are in place from Windsor through to Quebec City as record-breaking temperatures hit Central Canada.

Toronto set a new June 23 temperature record when the mercury hit 36 degrees.

Environment Canada says today’s temperatures will rival those seen yesterday, with the humidity expected to make it feel like upwards of 40 degrees in many cities under heat warnings.

Forecasters warn a heat dome this early in the season can be particularly dangerous since people are not acclimatized to the high heat and humidex values, which are well above normal.

Studies indicate that climate change, driven by the burning of fossil fuels, is increasing the length and intensity of Canadian heat waves.

This report by The Canadian Press was first published June 24, 2025.