A few summers ago, Gordon Gisbrecht was working on a lakeside pier when he said he was starting to feel “a bit funny”. Minutes later, he was vomiting – a symptom he immediately recognized as heat exhaustion.

An expert on how extreme temperatures affect the human body, Giesbrecht was the first to admit he should have seen the warning signs.

said Gesbrecht, professor of thermophysiology at the University of Manitoba.

In the midst of a heat wave warning Across much of Canada this week, Giesbrecht’s experience reminds us of how summer heat affects our bodies without us even realizing it – and the need to be on the lookout for life-threatening symptoms.

In Europe, more than 1,100 people have died from the heat in Spain and Portugal in recent days. There are also concerns for people elsewhere in Europe and the UK – places where there is little air conditioning to manage. Temperature above 30 degrees Celsius.

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Adding humidity to this heat makes it harder for us to cool down by sweating – and humans can actually cook alive.

“Our bodies can actually handle a 10 or even 20 degree drop in core temperature, but our body can only tolerate a 5 degree rise in core temperature. [to] Seven degrees – and then you could be in big trouble.

The warmer and more humid the water, the greater the risk of heat exhaustion. Symptoms include headache, profuse sweating, clammy skin, dizziness or confusion, seizures, rapid breathing, nausea, and vomiting. Among othersAccording to Health Canada.

Not (only) heat, but humidity

Scientists explain when the combination of heat and humidity becomes very dangerous, even deadly moist air temperature The lowest temperature to which an object can cool due to the evaporation of water vapor.

Imagine a thermometer wrapped in a damp cloth: water still evaporates from the cloth up to a certain level of humidity, while the air contains so much humidity that evaporation does not continue. Due to the effect of evaporation, the temperature of the thermometer will be lower than that of the surrounding air, that is, until the evaporation stops.

Our body works the same way: at a wet bulb temperature of 35°C (Like when it’s 40°C outside with 70% humidity), sweat no longer evaporates from our body, and Scientists predict That humans can live about six hours under these conditions.

“No matter how much water you have, it won’t help you because you can’t maintain a decent body temperature,” said Tapio Schneider, a climatologist and professor at the California Institute of Technology in Pasadena.

As your body temperature rises, your organs — including your heart, kidneys, and brain — begin to break down, and the proteins in your cells break down. A person with heat stroke can have seizures, coma and die.

The low temperature of a damp bulb can also be deadly, especially for the elderly, young children, and people with medical conditions. For example, during the European heat wave of 2003, which claimed the lives of more than 20,000 people, Wet bulb temperature stays below 28°C.

Even at this wet-bulb reading rate, it can be dangerous to do anything that can raise core body temperature, such as exercise or the kind of manual labor that Giesbrecht does when suffering from heat exhaustion. heat.

“If you’re working outdoors, working on a farm or working in construction on a hot, humid day…you run the risk of heat stroke, heart stress, etc.,” Schneider says. “Heat can be deadly before reaching that absolute survival limit.”

Stay calm and alert

With hotter, humid days this summer – and more days to come as the planet warms up – experts say people should limit the time they spend outdoors in the heat and use air conditioning to protect the space.

A fan is only useful if the air temperature is below your skin temperature of 33°C; If the air is warmer, the fan will raise the temperature even more, says Giesbrecht.

Staying hydrated will help you sweat, and spraying water on your body or clothes has a cooling effect on your skin as the water evaporates.

If someone experiences heat stroke, call 9-1-1 and move them to a cool place immediately, ideally an air-conditioned building or car. Symptoms include high body temperature, confusion and lack of coordination, dizziness or fainting, lack of sweating, red and very hot skin.

Instead of taking off someone’s shirt to cool them off, Giesbrecht advises pouring water on their clothes: Remember the wet ball effect?

“The water in the jersey will evaporate and cool the skin. If you don’t have a shirt on your skin, the water will roll off the floor.”

“I’m going to take a liter [of water] Pour it over the person, wait for it to dry, then I’ll add more so I can continue to use that vaporizing effect.”