During a heat wave, it is harder to cool down and keep your body temperature within normal limits. At these times, prolonged exposure to heat, excessive physical exertion or very heavy sweating can have certain effects on health.
Symptoms that require monitoring changes in health
Adults
It is important to monitor any deterioration in the health of an adult who has the following symptoms:
Headaches
Muscular cramps
Swollen hands, feet and ankles
Appearance of small red bumps on the skin, called a “heat rash”
Unusual fatigue or exhaustion
Generalized malaise
Signs of dehydration:
Intense thirst
Less frequent need to urinate
Dark urine
Dry skin
Rapid pulse and breathing
Nausea or vomiting
If you experience any of these symptoms, immediately go to a cool place and drink water.
If you have questions about your health, call Info‑Santé 811 or consult a health professional, a pharmacist for instance.
When to consult
Other symptoms, however, require immediate medical attention, meaning within 2 hours. An adult who has one or more of the following symptoms must be taken to the emergency room immediately or 9‑1‑1 must be called on their behalf:
Difficulty breathing
Convulsions (stiffness of the body and jerky, involuntary muscle contractions)
Signs of impaired consciousness:
Confusion
Unusual behaviour
Agitation
Hallucinations
No response to stimuli
Loss of consciousness
Signs of heat stroke:
Temperature over 39.5 ºC (103.1 ºF) with an oral thermometer or over 40 ºC (104 ºF) with a rectal thermometer
Dry, red, hot skin or pale, cold skin
Dizziness and vertigo
Confused and illogical speech
Aggressive or bizarre behaviour
Generalized malaise
Heat stroke is the most serious effect of heat. It can occur suddenly and quickly lead to death if not treated.
Babies or children
Certain symptoms may indicate the presence of heat-related complications:
Dry skin, lips or mouth
Abnormal skin colour (red or pale)
Headaches
Sunken eyes with dark rings
Dark and smaller quantity of urine
Vomiting, diarrhea
Unusual restlessness, irritability or confusion, temper tantrums
Difficulty breathing
Drowsiness, prolonged sleep and difficulty waking up
Body temperature over 38.5 ºC (101.3 ºF) with a rectal thermometer or over 37.5 ºC (99.5 ºF) with an oral thermometer (Note: Using an oral thermometer to take the temperature of newborns, babies and children under 5 years old is not recommended.)
When to consult
A child’s health, especially a very young child, can deteriorate quickly and be difficult to notice. When a baby or child shows symptoms, a medical consultation is usually necessary. If you are unsure, you can call Info‑Santé 811. In an emergency, call 9‑1‑1.
Protection and prevention
You can take certain precautions to prevent the effects of heat, such as drinking enough fluids and cooling off often. You will find other advice to ensure your well-being and that of your loved ones during a heat wave on the Preventing the effects of heat page.
Risk factors
The risk of feeling discomfort due to heat is higher:
When humidity is high
When there is light wind or none at all
When a heat wave occurs and the body is not used to the heat, such as early in the season or suddenly after a period of cooler weather
When the heat lasts for several days without a break
When temperatures are high during the night
In cities, where the temperature is generally higher than in the countryside
People at risk
Some people are more at risk of developing complications if they are exposed to heat:
Babies and children under 5 years of age
Older adults
People with reduced autonomy or who live alone:
People with reduced mobility
People with limited contact with family or friends
People suffering from chronic illnesses or severe mental health problems
People with drug or alcohol use problems
People with physically demanding jobs or who work in the sun or outdoors, such as construction workers or agricultural workers
People who work in places where processes emit heat, such as foundries or bakeries
People who do intense physical exercise outside in hot weather or indoors in places that do not have air conditioning or are poorly ventilated
People who do not have access to cool or air-conditioned places
People who take certain medications that can aggravate the effects of heat
People who are in poor physical condition or who are overweight
