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.

Toronto, southern Ontario and parts of Quebec are expected to see high levels of heat, and in some areas, it could be dangerous for people’s health. (The Canadian Press/Tijana Martin)

Toronto, the rest of southern Ontario and parts of Quebec are currently under a heat warning from Environment Canada. According to weather alerts released on Saturday morning, heat and humidity are coming this weekend — and, in some cases, it could pose serious threats.

“Dangerously hot and humid conditions will begin Sunday afternoon and is expected to continue into the week,” Environment Canada warned for the Greater Toronto Area and much of southwestern Ontario. That could look like daytime highs of 31°C to 36°C, with humidex values of 40 to 45.

Other parts of Ontario and areas of Quebec south of Montreal are under similar heat warnings expected to begin this weekend. Conditions are expected to last until Tuesday or Wednesday of this coming week.

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 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.

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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.

The first heat event of the season can pose serious health risks. (Image via Getty Images)

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.

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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?

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.

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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.

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.

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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.

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.

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.

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.

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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Dr. Brian Yuen, a family medicine physician at Inova-GoHealth Urgent Care, says the sizzling temperatures we’ve been seeing can impact how we feel.

If you’re feeling down or in a funk because of the extreme heat we’ve been experiencing, you’re not alone.

Dr. Brian Yuen, a family medicine physician at Inova-GoHealth Urgent Care, says the sizzling temperatures we’ve been seeing can impact how we feel.

“It’s not just hard physically on our bodies, causing dehydration and stress, but it affects our psychological well-being too,” Yuen said. “It affects our mood, it can increase stress levels, and it also can affect our sleep.”

One of his biggest recommendations is to get into a routine. Structure your day by waking up and going to bed around the same time and eating and exercising on the same schedule too.

“Basically, establishing what we call a good circadian rhythm, which is night and day routine,” Yuen said.

He said people generally sleep better in cooler weather so sticking to a schedule could help.

“So your body gets in this rhythm. It makes it easier to fall asleep. Just helps with your sleep, helps with your mood, helps reduce levels of anxiety, and can help you feel better overall,” he said. “Trouble sleeping can lead to worsening anxiety, depression and just general feelings of distress.”

And he said it’s still important to get a dose of sunshine. But in order to keep that safe, you need to watch when you go out.

“If you’re going to have to go outside and do outdoor activities, you want to do it generally before 11 a.m. or after 4 p.m.,” Yuen said.

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PHOENIX (AZFamily) — On the hottest day of the year so far, people in Phoenix were caught using anything they could to shield themselves from the sun.

“I do want to get out. I want to get out of the house and do things. I can’t walk the dog. The dog’s mad at me because she can’t go anywhere at this point,” said Mark Guidl.

Even longtime Phoenix residents said they need to hunker down out of the heat.

Banner Health Psychiatrist Dr. Tulasi Goriparthi said summertime sadness is a real phenomenon called Seasonal Affective Disorder (SAD).

He explained the heat can hurt our social life and throw off our bodies’ balance.

“The same chemicals in our brain that regulate the internal body clock that we have–the internal body temperature that we get regulated, the same chemicals are also implicated in causing depression or anxiety,” said Dr. Goriparthi.

Even when you’re trying to brave the heat, Dr. Goriparthi advices to be careful with over-hydrating.

“Because of the extreme heat, we have to drink lots and lots of water. That decreases our appetite. That brings more satiety into our stomach. A decreased appetite may increase fatigue. And that low energy levels combined with social isolation can trigger depression or anxiety,” he said.

If you are looking for a place to cool down, you can click/tap here to a map showing respite and cooling centers and hydration stations.

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During heat waves, emergency room visits and hospital admissions go up for people with diabetes, cardiovascular diseases, respiratory diseases, and mental health illnesses. [11]

Chronic medical conditions are those that last one year or more and either require ongoing medical attention, limit activities/daily living, or both.1 People with chronic medical conditions are more vulnerable than the general population to the health impacts of climate change because:

Some chronic medical conditions can increase an individual’s risk of illness and death when facing climate change-related impacts, particularly exposure to heat, extreme weather events, water-related illnesses, and poor air quality. 2, 3, 4, 5

when facing climate change-related impacts, particularly exposure to heat, extreme weather events, water-related illnesses, and poor air quality. People with chronic medical conditions often need consistent medication or medical care . Extreme weather events can disrupt care due to evacuations, transportation system or health infrastructure damages, or power outages. 6

. Extreme weather events can disrupt care due to evacuations, transportation system or health infrastructure damages, or power outages. Some medications for chronic conditions can affect the body’s response to heat, putting people at more risk for heat illnesses as the climate warms. 7

can affect the body’s response to heat, putting people at more risk for heat illnesses as the climate warms. Individuals with certain medical conditions can have compromised immune systems , which can make them more prone to extreme reactions related to heat, insect- and tick-related diseases, and water-related illnesses. 8, 9

, which can make them more prone to extreme reactions related to heat, insect- and tick-related diseases, and water-related illnesses. People with chronic mental illnesses are vulnerable to trauma from extreme weather events, as well as disruptions to support networks and mental health care.10

On this page:

Key Threats to the Health of People with Chronic Medical Conditions

A number of climate-related hazards threaten the health of people with chronic medical conditions. Below are some examples of the potential health impacts of these hazards.

Water-Related Illnesses

Harmful algal blooms can pose increased risks to people with chronic respiratory diseases. [21]

Climate change will impact water resources in many ways. For example, changes in water and air temperatures, heavier and longer rains, flooding, and rising sea levels can introduce disease-carrying organisms into drinking water supplies and recreational waters.14, 15

Drinking or coming in contact with untreated contaminated water can cause gastrointestinal illnesses and other health impacts.16 People with certain chronic medical conditions, such as those with compromised immune systems, can be more at risk of having severe effects from a water-related illness.17

Climate change may increase the likelihood of harmful algal blooms caused by certain types of algae and bacteria.18 Harmful algal blooms can make drinking and recreational water sources unsafe. For example, swimming in waters with a harmful algal bloom can cause respiratory illnesses and eye irritation.19 People with chronic respiratory diseases, specifically asthma, are at increased risk of illness from harmful algal blooms.20

Respiratory Illnesses

Climate change may increase outdoor air pollutants, such as ground-level ozone and particulate matter in dust from droughts and wildfire smoke.22 People with conditions such as hypertension, diabetes, and COPD are particularly vulnerable to adverse effects from exposure to these pollutants.

Climate-related rises in indoor dampness could worsen asthma. [27]

Climate change can also prolong the allergy season and increase pollen and other outdoor allergens. Data show the ragweed pollen season is already becoming longer in some U.S. locations.23 These allergens can worsen chronic respiratory conditions and contribute to the onset of asthma.24

Indoor contaminants, such as bacteria and mold, could also increase as the climate changes due to more humidity and dampness from frequent heavy rains, storms, and floods.25 Asthmatics and people with compromised immune systems are more vulnerable to indoor air pollutants than the general population.26

Overlapping Vulnerabilities Some people with chronic medical conditions may be part of other groups vulnerable to climate change. This can increase their health risks. For instance, low-income groups, people with limited English proficiency, certain immigrant groups, and communities of color have a greater incidence of chronic medical conditions such as heart and kidney disease, diabetes, asthma, and chronic obstructive pulmonary disorder (COPD).12 Black or African American populations have higher rates of asthma, decreased lung function, and heart issues.13 Older adults and children can also have chronic medical conditions.

Heat Illnesses

Heat-related illnesses can occur when a person is exposed to high temperatures and their body cannot cool down. Increases in average and extreme temperatures and heat waves are expected to lead to more heat illnesses and deaths among vulnerable groups, including older adults.28 Temperature extremes can worsen some chronic medical conditions, such as heart and respiratory disease and diabetes.29 At the same time, some medical conditions, such as obesity and heart disease, increase people’s sensitivity to heat, putting them at greater risk of heat illnesses.30 In addition, some medications (such as some antidepressants, diuretics, and beta-blockers) taken for a chronic illness may increase an individual’s sensitivity to heat by interfering with the body’s ability to regulate temperature, fluids, or electrolytes.31

West Nile virus is the leading cause of mosquito-related disease in the continental United States. [32]

Insect- and Tick-Related Diseases

Warmer temperatures associated with climate change can also increase mosquito development and biting rates, while increased rainfall can create more breeding sites for mosquitos.33

Mosquitoes can transmit diseases, such as West Nile virus. These diseases pose a greater risk to people with compromised immune systems, who may be more likely to experience severe illness.34 Most people do not develop symptoms with West Nile virus. However, some develop serious illness and even die.35

Studies show that climate change has already contributed to an expanded range for ticks.36 This could put more people at risk of contracting Lyme disease. Lyme disease can cause heart problems in some people.37 It can also cause chronic pain and neurological problems if not treated early.38

Extreme weather events can cause trauma that can worsen mental health disorders and disrupt personal support networks, health services, and treatment access. [39]

Mental Health Effects

As of 2022, approximately 59.3 million (more than one in five) U.S. adults live with a mental illness.40 Individuals with these conditions are particularly vulnerable to certain threats associated with climate change.41 For example, some medications used to treat mental illnesses increase a person’s risk for heat-related illness.42

Certain conditions, such as different types of dementia, can affect an individual’s judgment or reactions, increasing the risk of harm during a weather-related disaster.43 People with an existing mental illness are also more at risk for distress and other mental health effects following such an event.44