Extreme Heat Events

It's Your Health

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On this page:

• The Issue
• Extreme Heat Events
• Health Risks of Extreme Heat Events
• Reduce Your Risk
• Government of Canada's Role
• For More Information

The Issue

Many regions of Canada experience frequent and severe extreme heat events, sometimes called "heat waves" that can put your health at risk. It is important to take precautions to protect yourself and those you may be caring for.

Extreme Heat Events

During extreme heat events (as announced by  Environment Canada, or your local municipality/Health Unit) conditions of high temperature and/or humidity are present. Your body produces heat, especially during physical activity. Hot air and exposure to direct sun rays or hot surfaces also heat your body. This heat is lost by contact with cool air and by sweat production, which cools your body as it evaporates. Weather conditions play a big role in how your body regulates its temperature. For example, if it's windy, sweat evaporates faster, which helps to cool you. However, high humidity slows down this process, contributing to increased body temperature.

Health Risks of Extreme Heat Events

While extreme heat can put everyone at risk from heat illnesses, Heat-Vulnerable Groups:

• older adults
• infants and young children
• people with chronic illnesses, such as breathing difficulties, mental illness or heart conditions
• people who work in the heat
• people who exercise in the heat
• homeless people
• low-income earners

If you are taking medication or have a health condition, ask your doctor or pharmacist if it increases your health risk in the heat and follow their recommendations.

Heat illnesses can lead to long-term health problems and even death. These illnesses include heat stroke, heat exhaustion, heat fainting, heat edema (swelling of hands, feet and ankles), heat rash and heat cramps (muscle cramps) and are mainly caused by over-exposure to extreme heat or over-exertion for a person's age and physical condition.

Reduce Your Risk

Heat illnesses are preventable. During very hot weather, the most important thing is to keep cool and hydrated.

Follow these five steps to protect yourself in very hot weather

Step 1 - Prepare for the heat

Tune in regularly to  local weather forecasts and alerts so you know when to take extra care.

Arrange for regular visits by family members, neighbours or friends during very hot days in case you need assistance. Visitors can help identify signs of heat illness that could be missed over the phone.

If you have an air conditioner, make sure it works properly before the hot weather starts. Otherwise, find an air-conditioned spot close by where you can cool off for a few hours during very hot days. This will help you better cope with the heat.

Step 2 - Pay close attention to how you - and those around you - feel

Watch for symptoms of heat illness, which include:

• dizziness or fainting
• nausea or vomiting
• headache
• rapid breathing and heartbeat
• extreme thirst (dry mouth or sticky saliva)
• decreased urination with unusually dark yellow urine

If you experience any of these symptoms during hot weather, immediately move to a cool place and drink liquids. Water is best.

Heat stroke is a medical emergency! Call 911 or your local emergency number immediately if you are caring for someone, such as a neighbour, who has a high body temperature and is either unconscious, confused or has stopped sweating.

While waiting for help - cool the person right away by:

• moving them to a cool place, if you can
• applying cold water to large areas of the skin or clothing
• fanning the person as much as possible

Step 3 - Stay hydrated

Drink plenty of cool liquids, especially water, before you feel thirsty to decrease your risk of dehydration. Thirst is not a good indicator of dehydration.

• Remind yourself to drink water by leaving a glass by the sink
• Flavouring water with natural fruit juice may make it more appealing
• Eat more fruits and vegetables as they have a high water content
• If you eat less, you may need to drink more water

Step 4 - Stay cool

Dress for the weather - Wear loose-fitting, light-coloured clothing made from breathable fabric.

Keep your home cool

• If you have an air conditioner with a thermostat, keep it set to the highest setting that is comfortable (somewhere between 22°C/72°F and 26°C/79°F), which will reduce your energy costs and provide you with needed relief.
• If you are using a window air conditioner, cool only one room where you can go for heat relief.
• Prepare meals that don't need to be cooked in your oven.
• Block the sun by closing awnings, curtains or blinds during the day.
• If safe, open your windows at night to let cooler air into your home.

If your home is extremely hot

• Take a break from the heat by spending a few hours in a cool place. It could be a tree-shaded area, swimming facility or an air-conditioned spot such as a shopping mall, grocery store, or public library.
• Take cool showers or baths until you feel refreshed. Make sure to use non-slip surfaces in the tub and shower, and wipe up moisture immediately to avoid slipping and falling.
• Use a fan to help you stay cool and aim the air flow in your direction.

Step 5 - Avoid exposure to very hot temperatures when outdoors

Never leave people or pets in your care inside a parked vehicle or in direct sunlight.

• When outside air temperature is 23°C/73°F, the temperature inside a vehicle can be extremely dangerous - more than 50°C/122°F.

Reschedule or plan outdoor activities during cooler parts of the day.

• Before heading out, check the  Air Quality Health Index (AQHI) in your area, if available - air pollution tends to be at higher levels during very hot days.
• If you are in an area where mosquitoes are active, protect yourself with insect repellent and follow the manufacturer's directions.

Avoid sun exposure. Shade yourself by wearing a wide-brimmed, breathable hat or using an umbrella.

• Tree-shaded areas could be as much as 5ºC/9ºF cooler than the surrounding area.
• Use a sunscreen that is SPF 15 or higher and follow the manufacturer's directions. Remember, sunscreen will protect against the sun's ultraviolet (UV) rays but not from the heat.
  • Sunscreen and insect repellents can be safely used together, apply the sunscreen first, then the insect repellent. Sunscreens and insect repellents work for different lengths of time so follow the instructions on the label.

Government of Canada's Role

Health Canada is committed to maintaining and improving the health of Canadians. We are working with our partners to better understand the impacts of extreme heat on the health of Canadians, particularly those at greatest risk, and to promote efforts to reduce these risks. We provide information to Canadians on steps they can take to maintain and improve their health, including information on how they can prepare themselves to adapt to prolonged periods of extreme heat.

For More Information

• For weather conditions in your area go to Environment Canada's  Weather Office
• Health Canada's Extreme heat video
• Health Canada, Safe Summer Fun
• Health Canada, It's Your Health, Summer Information section
• Health Canada's Sun Safety section
• Environment Canada and Health Canada's  Air Quality Health Index
• Health Canada, Climate Change and Health

Related Resources

• Health Canada, It's Your Health - Insect Repellents
• Health Canada, It's Your Health - Sunscreens
• Public Health Agency of Canada's -  Canada's Physical Activity Guide to Healthy Active Living
• For safety information about food, health and consumer products, visit the Healthy Canadians website
• For more articles on health and safety issues go to the It's Your Health web section

You can also call toll free at 1-866-225-0709 or TTY at 1-800-267-1245*