"A cold front will usher in a slightly cooler air mass for (Monday)".
"A cold front is going to come Thursday night, and that will drop our temperatures back to more normal ones, especially for this weekend", says Cheng.
However, daytime highs are still expected in the low thirties in the next two days.
In the Eastern Townships region southeast of Montreal, four deaths are under investigation to determine if they are related to the extreme heat.
Lows in the 20s continue to provide "little or no relief from the heat", the agency said.
Toronto's Medical Officer of Health extended the city's heat warning until further notice over the weekend.More news: EU warns U.S. of boomerang effect if Trump imposes car levies
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The heat warning extends throughout the GTA and most of southern Ontario, including Hamilton, Waterloo and Barrie.
Environment Canada has issued heat warnings for parts of northern Ontario and all of the southern part of the province.
Humidex values reaching 43 are expected.
A warm and humid airmass has settled over the Maritimes and will persist until the middle of the week. However, the risks are greater for young children, pregnant women, older adults, people with chronic illnesses and people working or exercising outdoors. "And also do not forget to make sure you don't leave any people or pets in your vehicle, as temperatures will rise dramatically within minutes".
According to the weather network, the ongoing forecast with temperature highs above 30 C is "the most significant heat event in the past few years" and it has no sign of slowing down. Watch for the effects of heat illness: swelling, rash, cramps, fainting, heat exhaustion, heat stroke and the worsening of some health conditions.