Humidity makes a sweltering apartment that much harder to live in

On a hot summer day, the air in Sridharan Vankeepuram's room can be nearly unbearable.

"It feels like a furnace inside," he said.

His small bedroom — crammed with a single bed and a desktop computer — doesn't get much cooler at night, especially when it's humid, as is often the case during a Montreal heat wave.

"It becomes really uncomfortable. When you close your eyes, you just start sweating."

Vankeepuram has spent the past two years in an aging brick building on the western edge of Montreal's downtown, while completing his MBA at Concordia University. The three-storey walkup faces the old Montreal Forum, which reflects the sun back through his window.

A few sparse trees along the block do little to counter the sun, and he has only a small oscillating fan to keep cool.

One day in July, Vankeepuram's room felt like it was 39 C when taking the humidity into account, the highest heat index of any home measured as part of CBC's country-wide urban heat project.

(For this project, CBC used heat index to measure the combination of air temperature and humidity, rather than the humidex, a similar index developed in Canada.)

To better understand the challenges of living in extreme heat as the climate changes, this summer CBC News installed sensors in 50 homes that were either wholly or partly without air conditioning across five Canadian cities, including Montreal.

The sensors took temperature and humidity readings every 10 minutes. In some places, particularly in apartments in Toronto, Windsor and Montreal, the humidity made the residences feel much hotter. Winnipeg and Vancouver, which tend to have drier heat, were the other two cities featured in the project.

For half of the 56 days measured, Vankeepuram's room didn't drop below 26 C, the threshold considered dangerous for seniors and those with pre-existing conditions if they are exposed to it for a prolonged period.

And Vankeepuram's room consistently felt even warmer because of the humidity.

Knowing he would move out after graduating, Vankeepuram didn't invest in an air conditioner. On the worst days, he took multiple showers or brought a bucket of ice water into his room.

For others, the consequences can be more dire. Humans cool down by sweating, but when the air is saturated with moisture, that doesn't work as well.