Temperatures in Canada have hit 40°C for the first time this summer. How extreme heat can impact your body — and how to stay cool

With heat warnings in effect across the country, millions of Canadians at risk for heat-related illnesses.

This article is for informational purposes only and is not a substitute for professional medical advice, diagnosis or treatment. Contact a qualified medical professional before engaging in any physical activity, or making any changes to your diet, medication or lifestyle.

Woman cooling down splashing herself with bottle of water on a hot sunny day.
Temperatures will reach the high 30s across Canada this week. (Image via Getty Images)

Canada has reached its first milestone for summer. Over the weekend, Ashcroft, B.C. registered the first 40-degree temperature of 2024 — with more high temperatures expected to follow across the country.

According to Environment Canada, Alberta and parts of British Columbia will experience temperatures in the high 30s and low 40s due to a "ridge of high pressure." Temperatures are expected to drop into the teens at night, with daytime highs expected to remain high through Wednesday.

Heat warnings have been issued for Saskatchewan and parts of eastern Canada as humidex values bring temperatures into the high 30s.

The heat poses serious health risks to children, the elderly, people with chronic health conditions and unhoused populations.

Mature woman is feeling bad during the heat wave in city
The first heat event of the season can pose serious health risks. (Image via Getty Images)

Extreme heat can impact different parts of our bodies in different ways, including heat stroke and heat exhaustion. Keep reading to learn more.


As temperatures increase, the body has to work overtime to try and get rid of extra heat. According to an article in Harvard Health Publishing, on a hot and humid day, the heart may circulate two to four times as much blood each minute to try and shed excess body heat. The extra stress on the heart can increase the chances of heart failure, irregular heartbeats and heart attacks —especially if you have a pre-existing health condition.

If you have damage from a heart attack or narrowed arteries due to cholesterol, the heart may not be able to pump enough blood to help cool you down. Additionally, medications like beta-blockers can “interfere with heat regulation” by limiting the heart’s ability to pump blood fast enough.


Senior Man With Chronic Bronchitis is Using Inhaler.
How does extreme heat impact people with COPD? (Image via Getty Images)

Heat, humidity, air pollution and smog are a dangerous combination for anyone, but especially for people with compromised respiratory systems.

According to the Canadian Lung Association, people with asthma or chronic obstructive pulmonary disease (COPD) are encouraged to seek out spaces with clean air and air conditioning on hot and humid days. Staying inside with air filters or in smoke-free, scent-free public spaces like shopping malls, can help prevent irritants triggering an asthma attack or worsening COPD symptoms.

Because people with COPD already utilize extra energy to breathe, their bodies now have to work overtime to not only breathe, but regulate body temperature. What’s more, extreme changes in weather can trigger bronchospasms, a narrowing of the airways, which makes it difficult for people with COPD to breathe.

In an interview with Bayhealth, Dr. Michael Samaha recommended staying inside as much as possible to avoid compromising your breathing. However, if you do have to go outside, consider wearing a mask to protect yourself from air pollutants.

“Not everyone is affected the same way,” Samaha said. “It can depend on the severity of [the] disease or the air quality. That’s why the best course of action is to avoid going outside if you can.”


During a heatwave, our entire body is working overtime to keep us cool, including our kidneys. For people with chronic kidney disease, sweating and dehydration can put pressure on the kidneys and compromise their function. If your kidneys are damaged enough, this could cause kidney failure.

teenager holding two cold bottles of water while walking outdoors
Dehydration is a serious health risk for people with kidney disease or chronic kidney issues. (Image via Getty Images)

A 2017 review found that kidney-related deaths increase by 30 per cent during periods of extreme heat.

According to the U.S. National Kidney Foundation, staying hydrated and keeping your body temperature below 40°C (104°F) is crucial to avoiding heat-related illnesses. Avoid drinking liquids or alcohol that could act as a diuretic and be sure to relocate to areas with air conditioning or, at the very least, an electric fan.


Heatstroke or heat exhaustion can manifest itself in different ways. People who may be experiencing heat-related illnesses may seem confused or disoriented. Studies have found that heat stress reduces blood flow to the brain which can impact our judgement and decision making and put ourselves at risk of injury.

The man sitting in the corner of the room has emotional and mental problems He has depression and stress from society and work. medical concept.
Heatwaves have been linked to an increase in suicides. (Image via Getty Images)

Extreme temperatures and humidity also cause disruptions in sleep patterns — which can take a toll on mental health, and increase irritability, symptoms of depression and may cause some people to become aggressive.

People with existing mental health issues are also considered vulnerable during heat waves. A 2023 meta-analysis published in the Lancet noted that heatwaves have been linked to an increase in hospital admissions for mental health-related emergencies and an increase in suicides.


People with diabetes have to be diligent when it comes to monitoring their diabetes, especially during a heat event. Glucose levels can be impacted by heat stress and people with diabetes may have a compromised ability to get rid of excess body heat.

Blood sugar finger prick testing with portable glucometer.
Avoid keeping your diabetes glucose meter, test strips or insulin in the heat. (Image via Getty Images)

People with diabetes face serious health risks during extreme heat. A 2016 report found that people with type 2 diabetes, specifically, have a 56 per cent greater chance of death or requiring hospitalization during a heatwave.

In an effort to stay healthy, people with diabetes who spend time outside are encouraged to store their test strips and insulin in cooler bags to prevent heat damage. Along with staying hydrated, it's a good idea to increase the number of glucose checks per day to ensure their blood sugar levels are within a healthy range.


It's important to have a plan in place to everyone stays safe when temperatures and humidex values skyrocket.

  • Avoid spending time outside

  • Stay in air-conditioned areas when possible

  • Visit public air-conditioned spaces like shopping malls, local libraries and civic centres to stay cool

  • Drink water; Avoid drinks that could act as a diuretic

  • Take cool showers

  • Cool yourself with a cold towel or spray bottle

  • Use electric fans to get air circulating in non-air-conditioned spaces

  • Check in with elderly friends and family members or anyone vulnerable during heatwaves

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