During a heat wave, the body has greater difficulty maintaining a normal temperature. Prolonged exposure, intense physical effort and dehydration can cause illness and, in severe cases, potentially fatal heat stroke.
This guide explains who is most at risk, how to stay cool, the early warning signs of heat-related illness and when heat becomes a medical emergency.
Key takeaways
- Young children, older adults, pregnant people, people living alone and people with chronic illness are at higher risk.
- Some medicines can affect the body’s response to heat. Do not stop medication on your own; ask a physician or pharmacist.
- Drink water regularly without waiting until you feel thirsty, and spend at least two hours per day in a cool place if possible.
- Early warning signs include headache, muscle cramps, unusual fatigue, nausea and intense thirst. Call Info-Santé 811 if you are unsure.
- Confusion, seizures, loss of consciousness or a very high body temperature may indicate heat stroke. Call 9-1-1 immediately.
Who is most at risk during a heat wave?
Babies, young children, older adults, pregnant people and people with chronic illness are among those most at risk during extreme heat. Higher-risk groups include:
- Babies and children younger than five, older adults, pregnant people and individuals who live alone or have reduced independence.
- People with chronic illness, serious mental health conditions or reduced mobility.
- People who work or exercise intensely outdoors and those who do not have access to a cool or air-conditioned location.
Can medications make heat more dangerous?
Some medicines, including diuretics, antidepressants, sleeping pills, antipsychotics and diabetes medications, can affect the body’s response to heat. Do not stop medication on your own; ask a physician or pharmacist for advice.
How can you stay cool and protect yourself during a heat wave?
Drink water regularly, cool your body down, spend time in a cool place and reduce exertion during the hottest hours.
Stay hydrated
- Drink water regularly without waiting until you feel thirsty.
- If you have been prescribed a fluid restriction, ask your healthcare professional how to adjust hydration during hot weather.
- Avoid alcohol, which can worsen dehydration.
Cool your body down
- Cool down with a cool shower or bath, wet cloths or a spray bottle.
- If possible, spend at least two hours per day in an air-conditioned or cool location.
Dress and plan activities for the heat
- Wear lightweight, loose, pale-coloured clothing and a wide-brimmed hat.
- Reduce exertion and schedule physical activities during cooler hours.
Keep your home cooler
- Close curtains and blinds while the sun is shining.
- Ventilate when the outdoor temperature becomes cooler than indoors.
- Limit the use of ovens, dryers and other heat-producing appliances.
Never leave anyone in a parked vehicle
Never leave a child or pet alone in a vehicle, even for a few minutes and even with the windows open.
What are the early warning signs of heat-related illness?
Headache, muscle cramps, unusual fatigue, nausea, intense thirst, dry skin, dark or less frequent urine and rapid breathing can be signs of heat-related illness.
If someone shows these signs:
- Move the person to a cool place.
- Allow them to rest.
- Cool the skin.
- Offer water if they are fully alert and able to drink normally.
- Call Info-Santé 811 if you are unsure or the condition worsens.
What are the signs of heat stroke, and when should you call 9-1-1?
Confusion, unusual behaviour, seizures, loss of consciousness, breathing difficulty or a very high body temperature may indicate heat stroke. Call 9-1-1 immediately.
While waiting for help:
- Move the person to a cool place.
- Begin cooling.
- Do not give fluids to someone who is confused, very drowsy or unconscious.
Early warning signs vs. heat stroke: what to do
Early warning signs
- Signs: Headache, muscle cramps, unusual fatigue, nausea, intense thirst, dry skin, dark or less frequent urine and rapid breathing.
- What to do: Move to a cool place, rest and cool the skin. Offer water if the person is fully alert and able to drink normally. Call Info-Santé 811 if unsure or worsening.
Possible heat stroke
- Signs: Confusion, unusual behaviour, seizures, loss of consciousness, breathing difficulty or a very high body temperature.
- What to do: Call 9-1-1 immediately. Move the person to a cool place and begin cooling. Do not give fluids if the person is confused, very drowsy or unconscious.
Prepare before the next heat wave
At Bina Clinic, we encourage everyone to prepare before very hot days by identifying a cool place, keeping water available, adjusting activities and checking regularly on vulnerable relatives and neighbours.
If you take a medication that can affect your body’s response to heat, a physician can review it with you before summer.
Official sources
This article provides general information and does not replace a personalized medical assessment, diagnosis or treatment.
