Heat warnings in effect for Ontario, Alberta and more: What to know about weather alerts and how extreme heat impacts the body
Temperatures are creeping higher and higher, but just because there isn't a heat warning in your area doesn't mean you should let your guard down.
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.
It's almost August, and even though we're halfway through summer, the heat is still ramping up. Heat warnings have been issued for Toronto and parts of the golden horseshoe as temperatures are expected to reach a maximum of 30 to 32°C with humidex values near 40°C.
Similar heat warnings are in effect for northern Ontario, parts of Alberta and parts of Newfoundland.
It's hot — why isn't there a heat warning in my area?
Environment Canada has different threshold criteria for different regions of each province and territory that must be met to issue weather alerts for heat. Heat warnings are typically issued when daytime temperatures reach a minimum set point for two or more consecutive days.
For example, in southern Ontario, a heat warning is issued when daytime temperatures are expected to reach 31°C or warmer for two or more consecutive days and "nighttime minimum temperatures are expected to fall to 20°C or warmer.” Alternatively, a heat warning can be issued for the same area when humidex values are expected to reach 40°C or higher for two or more days.
How extreme heat can impact your body
But just because a heat warning isn't in effect doesn't mean the temperatures don't pose serious health risks, especially for children, the elderly, people with chronic health conditions and unhoused populations. Temperatures can still be dangerously high — they just don't meet Environment Canada's criteria for a weather alert.
Extreme heat can impact different parts of our bodies in different ways, including heat stroke and heat exhaustion. Keep reading to learn more.
How does extreme heat impact your heart?
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.
How does extreme heat impact your lungs?
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.”
How does extreme heat impact your kidneys?
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.
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.
Is extreme heat bad for your mental health?
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.
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.
Is extreme heat dangerous for people with diabetes?
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.
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.
What can you do to stay safe (and cool) during a heatwave?
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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