Hot temperatures sparked heat warnings in parts of Saskatchewan, Manitoba, Ontario, Quebec and adjacent provinces.
The increase came suddenly after a prolonged warm spell in Ontario, its longest since 1934, with 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 at the start of the week before rain starts Tuesday.
Authorities advised residents to avoid the sun when danger is highest.