The heat warning is expected to end on Wednesday, but then an entirely different - though no less unsafe - weather front will move in, with a chance of thunderstorms hitting Calgary by Wednesday afternoon.
The city's heat warning ended on Tuesday morning.
Environment Canada has ended its heat alert for the City of Toronto and surrounding areas after another days-long heat wave gripped southern Ontario.
"Scattered thunderstorms will affect the region today".
"Daytime maximum temperatures are expected to be the low 30s with humidex values near 40", the agency warns.
The City of Toronto also issued its own warning over the weekend following prolonged heat and humidity.
Sikome Lake was packed Monday with sun worshippers as temperatures hovered around 30 C
Overnight lows aren't expected to drop below 20 C in the urban districts.
Some slightly cooler weather is in store beginning mid-week as an upper level trough moves into the interior, it adds.
The risk is higher for young kids, pregnant women, older adults, people with chronic illnesses, and people who work or exercise outside.
It's also recommending not to leave people or pets inside a closed vehicle for any length of time.
Symptoms of heat stroke or heat exhaustion include high body temperature, lack of sweat, confusion, fainting and unconsciousness.
The Lake Cowichan Fire Department posted about the upgraded danger rating to Facebook and reminded campers to make sure campfires are fully extinguished.