Numerous victims were older than 50, male, living alone and had no air conditioning, said Dr. David Kaiser of Montreal's Regional Public Health Department.
Kaiser said the social aspect - living alone and not having another place to go to cool down - typically plays a major role in heat-related deaths in the city.
Health authorities reported that the number of heat casualties increased to 50 people.
A heat wave in the southern part of the Canadian province of Quebec has been linked to 54 deaths, officials say.
The sweltering weather began last Friday with temperatures hitting 35 degrees Celcius with high humidity.
"Looking at the weather forecast, we are waiting for a return to normal in the coming hours", said Health Ministry spokeswoman Noemie Vanheuverzwijn.
While temperatures have come down on Friday, public health officials are warning that the Quebec residents should still take precautions in the wake of a week-long heatwave that claimed at least 44 lives throughout the province. The temperature of the air in their homes reached 38 degrees.
Drouin said the victims were part of "the very vulnerable population, the elderly or people suffering from chronic or mental illnesses".
No deaths have been reported in other provinces.
But Ontario does not track heat related deaths in the same way as Quebec and does not report on potential causes of death without a coroner's investigation.
The ambulance service that serves a large swath of the Montreal area has called on people to refrain from calling unless it is a real emergency.