OTTAWA, Ontario — Health authorities in the Canadian province of Quebec said Thursday that 33 people have died from heat-related complications in the last few days.

Eighteen of those deaths have come in Montreal, where humid temperatures climbed past 110 degrees Fahrenheit (43 degrees Celsius).

Many of the victims were men over the age of 50 living alone in private apartments and seniors' residences, according to Dr. David Kaiser with Montreal's public health department.

None of the victims had air conditioning and Kaiser said most of them died inside of their homes.

"It's not surprising," he said. "Heat risk in an urban setting is a combination of medical, social and environmental exposures. The elderly, people with chronic diseases and people with mental health problems are more at risk."

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.

"Montreal is gigantic heat island," he said, referring to an environmental phenomenon caused by a lack of vegetation and an abundance of concrete. There also micro heat islands throughout the city, particularly in some of the poorer areas, he added.

This, too, played a factor in the current heat wave, which began June 29.

Heat warnings were in effect across southern Quebec, Ontario and the Atlantic region of the country, but temperatures were expected to drop overnight.

Dr. Mylene Drouin, the regional director of Montreal's public health department, said ambulance services reported receiving more than 1,200 calls overall in Montreal on Wednesday.