Temperatures are expected to climb ever higher Tuesday with an expected high of 36 C.
Those signs include swelling, rashes, cramps and fainting and those out in the sun are urged to drink plenty of water before they feel thirsty - and stay in a cool place to keep from overheating.
Environment Canada released a statement warning of a severe thunderstorm watch Monday morning.
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. Strong wind gusts can toss loose objects, damage weak buildings, break branches off trees and overturn large vehicles.
Residents are reminded to stay indoors when there is a severe thunderstorm in the area.
The Office of the Fire Marshal and Emergency Management recommends that you take cover immediately if threatening weather approaches. Air quality may deteriorate if the smoke descends to ground level. Seniors, children, persons with medical conditions as well as other vulnerable individuals are especially at risk.
Cooler temperatures and another slight chance of showers are in the forecast for this weekend, though for the most part, it should be nothing but pleasant - if somewhat cloudy - summer days.
It's also important to be aware of the risks of the extreme heat if you are working or exercising outdoors.