TORONTO — Parts of Ontario and Quebec will be slammed with "dangerously hot" temperatures for at least the next few days.
Environment Canada issued its first significant heat warning of the season on Saturday for southern and eastern Ontario and southern and western Quebec.
The agency said hot and humid conditions will begin in Ontario's far south, including Windsor, and will likely continue until Wednesday.
Areas a bit further north, including Toronto and eastern Ontario, are expected to feel the heat on Sunday.
Daytime highs are forecast to hit 31 C to 36 C, with the humidex making it feel more like 40-50 degrees.
The weather agency says a cold front is expected to push through late Tuesday, but noted it's uncertain how far south it will reach.
It says that could mean the higher temperatures extend into Wednesday in southwestern Ontario.
In Quebec, a warm and humid air mass will gradually move over the southern part of the province starting Sunday and will ease on Wednesday.
Maximum temperatures will exceed 30 C during the day and remain above 20 C at night. The brunt of the heat will come Monday and Tuesday, when humidex values will make it feel like 40-to-45 C.
People are encouraged to stay hydrated by drinking water before they're thirsty and to watch for early signs of heat exhaustion.
Environment Canada's seasonal forecast says the summer is expected to be hotter and more humid than normal across Ontario.
Studies have shown human-caused climate change, driven by the burning of fossil fuels, is increasing the likelihood and length of Canada's heat waves.
This report by The Canadian Press was first published June 21, 2025.
David Friend, The Canadian Press
