A new report by Statistics Canada says deaths in the country's 12 highest-population cities go up on days when there is extreme heat.
The study says people aged 65 and older are the hardest hit.
Cities with larger proportions of people renting their homes had higher risks of death during extreme heat events.
Seniors in both Montreal and Toronto had higher rates of deaths due to respiratory causes on extremely hot days.
The study also found that the risk of heat-related deaths was higher in cities where people aren't used to extreme heat, including Vancouver and Surrey, B.C.
The report looked at daily mortality data for two decades between 2000 and 2020.
The cities included in the study were Brampton, Ont.; Calgary; Edmonton; Hamilton; Mississauga, Ont.; Montreal; Ottawa; Quebec; Surrey, B.C.; Toronto; Vancouver and Winnipeg.