Hot temperatures prompted heat warnings throughout parts of Saskatchewan, Manitoba, Ontario, Quebec and nearby regions.
The rise came suddenly after a long hot stretch in Ontario, its longest since 1934, with the humidex making it feel hotter still.
Manitoba also broke a daily high mark temperature record during the same stretch.
Metro Vancouver hit nearly 31 C early in the week earlier this week before rain starts Tuesday.
Officials advised residents to stay out of the sun when danger peaks.