Heat warnings have been issued for parts of Alberta and British Columbia, bringing the total number in effect across Canada to 110.
Overnight minimum temperatures will only fall to near 20°C, providing little relief from the heat.
High temperatures mean big health risk for young children, pregnant women, the elderly, people with chronic diseases and those who work outdoors.
"Daytime maximum values of 31 degrees or higher are expected on both Sunday and Monday with Humidex values near 40", Environment Canada meteorologists said Saturday.
The city of Montreal has announced that some of its outdoor aquatic facilities, including splash parks, will have extended opening hours.
It was issued on Friday, and is expected to last until a cold front moves in on Tuesday.
It says never leave any person or pet inside a closed vehicle, for any length of time.
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