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Heat warning for southern Ontario is expected to last into Thursday

Southern Ontario is expected to experience temperatures of up to 32 C, with the humidex making it feel like up to 40 C during the day. Environment Canada's heat warning says the heat wave could last for the better part of a week, with the hottest day expected to be Saturday.

Toronto could reach temperatures of up to 32 C Friday, weather agency says

The Canadian Press ·
Torontonians watch the sunset at Woodbine Beach on June 23, 2025 — the first day under an Environment Canada heat warning.
A view of Woodbine Beach on June 23 when Toronto was under a different heat warning. Environment Canada issued a new warning Friday that covers much of southern Ontario. (Evan Mitsui/CBC)

Environment Canada has issued a heat warning for southern Ontario, saying hot and humid conditions could last into Thursday.

The alert issued Friday morning says daytime highs for areas between Windsor and Cornwall are expected to range from 29 C to 32 C, with the humidex making it feel like it's 35 C to 40 C.

Overnight lows are expected to provide little relief, ranging from 19 to 23 degrees.

The weather agency says the hottest day is expected to be Saturday and a shift in weather patterns on Thursday is expected to end the long stretch of heat and humidity.

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 is the third heat warning issued for southern Ontario this summer, including extreme heat that broke records in June.

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