View an interactive map of the transit heat here

MONTREAL - If you rode a bus or métro in Montreal on Thursday, chances are you arrived at your destination hot, damp – and more than a bit cranky.

The searing temperatures on the Société de transport de Montréal’s transit network are a reality of life in this city.

For a few horrible days every summer, the island bakes as temperatures soar into the mid-30s or higher, and our transit system heats up right along with it. The STM network is, for the most part, not air-conditioned, and to make matters worse, the métro tunnels seem to actually trap the heat – ensuring commuters stay sweltering hot for days after the air above ground has cooled.

On Monday, a Gazette reporter witnessed a young woman collapse in a métro car on the Green Line, leaving her toddler screeching in terror as fellow passengers tried to rouse his mother. She eventually regained consciousness, explaining she had been overwhelmed by the heat.

“It must be 30C in here,” said one concerned rider, shaking her head.

It could easily have been 30C. Or 25C. Or perhaps 35C.

The fact is, Montrealers complain that our transit system is too warm, but most of us have no sense of the actual ambient temperature on a bus, métro car or in a subway station when the mercury spikes like it has this week. Is it hotter than the temperature outside? Is it actually cooler, but we feel warmer because there’s very little air circulating? Is it hot enough to be a public health concern?

On Thursday, as temperatures peaked at 35C, and it felt like 45 with the humidex, The Gazette sent four reporters out with identical digital thermometers to take temperature readings on the STM network during the hottest part of the day (noon to 3 p.m.) and again during the afternoon-rush hour. They also took readings at other locations throughout the city as a means of comparison. The results showed that in many cases, the temperature (without the humidity factored in) exceeded the temperature outside – in one instance hitting 38C.

According to Dr. Louis Jacques of Montreal’s public health department, the temperatures may seem alarming, but the length of exposure is the critical factor.

“We know that the length of time during which people are exposed to the heat on public transit is generally short, since they are on their way somewhere, and often it’s somewhere that is air-conditioned,” he said. “You can be in a very uncomfortable situation for a short amount of time. ... We’ve never seen a report or case of a death (during a heat wave) on public transit.

“The greatest majority of heat-related deaths occur at home.”

This month, the STM began asking commuters on the city’s handful of air-conditioned buses if they would be willing to pay higher fares for cooler air throughout the bus network. It was an unusual step, considering that both the city and the STM have always maintained that the price of installing cooling systems is just too steep. Air conditioning also increases fuel consumption and that would run contrary to the city’s goal of reducing greenhouse gas emissions.

On the other side of the debate, however, are those who say that packing 50 or more people into a métro car or bus with no air conditioning during the summer months dissuades people from using public transit.

For the time being, Jacques said, all commuters can do is follow the standard advice during a heat wave.

“Drink plenty of water ... and if a person starts to feel unwell, they can usually get out of the vehicle fairly quickly.”

mmuise@montrealgazette.com