Environment Canada says a multi-day heat event for parts of Ontario and Quebec is set to begin on Sunday with a humidex that will make it feel like it's as high as 42 C.
The weather agency issued the heat warning on Saturday afternoon, saying people can expect daytime highs ranging between 30 and 34 C.
It says overnight low temperatures are expected to range between 19 and 23 C, providing little relief from the heat.
The heat wave is expected in all of southern Ontario along Lake Erie and Lake Ontario and across a stretch of Quebec to the Trois-Rivières area.
It's yet another heat warning for Ontario this summer, where last month temperature records in many parts of the province were broken during an extreme heat wave.
During heat warnings, people are advised to drink water often, watch for signs of heat exhaustion and to check on older adults and those at risk of heat illness.
This report by The Canadian Press was first published July 26, 2025.
The Canadian Press
