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Extreme Temperatures

Extreme Heat and Your Health

Severe Cold Weather

Extreme Heat and Your Health

This page was reviewed or revised on Wednesday, November 04, 2009 1:39 PM


PDF of Fact Sheet dated May 26 2009

What is extreme heat?

In Canada, the humidex is a term used to express the combined effect of heat and humidity. Environment Canada issues a Humidex Advisory when temperatures are expected to reach or exceed 30°C, or if the humidex is expected to reach or exceed 40°C.

Extreme heat and your health

As the humidex value increases, it becomes harder for the human body to regulate its temperature.

Extreme heat can affect your health many ways: heatstroke, heat exhaustion, dehydration, fatigue, cramps.

Heatstroke is the most serious heat-related illness. It occurs when the body is unable to control its temperature. When the body loses its ability to cool itself, the core body temperature rises rapidly. Heatstroke can cause permanent damage to vital organs and may lead to death if emergency treatment is not provided.

Heat exhaustion is a milder form of heat-related illness that may develop after several days of exposure to high temperatures and inadequate replacement of fluids.

(See Table 1 for signs and symptoms of heat-related illness.)
Please click here to view Table 1, page 2 of the Fact Sheet

Who is at risk?

  • Seniors
  • People with chronic conditions, such as lung and heart disease
  • People who are obese or overweight
  • Infants and very young children
  • Homeless people
  • People who work or are active in a hot environment

How can I protect myself?

  • Limit your time outdoors between 11 a.m. and 4 p.m., when the UV index is most intense.
  • Drink lots of water and natural juices, even if you do not feel thirsty.
  • Avoid drinking alcohol, coffee and cola.
  • Electric fans may provide comfort, but they do not prevent heat-related illness during extreme heat events.
  • Seek an air-conditioned setting. If you do not have air conditioning in your home, go to a shopping mall, library or recreational facility.
  • If you are unable to visit an air-conditioned facility, take a cool shower or bath and keep the curtains or blinds drawn during the hottest part of the day.
  • Wear lightweight, loose-fitting clothing. When outside, wear a wide-brimmed hat and sunglasses.
  • While outdoors, seek shade when possible.
  • Avoid intense physical activity.
  • Check with your doctor about the side effects of your medication that may make you more vulnerable to extreme heat.
  • Check on children, seniors, persons with disabilities and individuals with chronic illness; ensure they are well hydrated and do not show signs of heat-related illness.
  • Never leave anyone (including pets) in a closed, parked vehicle.
  • Be aware of the signs and symptoms of heat-related illness. Seek medical attention if necessary.
  • Apply sunscreen SPF 15 or higher, 20-30 minutes before going outside.

Table 1: Signs, symptoms and treatment for heat-related illnesses. (Please click here to view the Fact Sheet in PDF on page 2)

For more information about extreme heat, call County of Lambton Lambton Public Health at 519 383-8331 ext. 3601, or toll free at 1-800-667-1839.

Html and PDF dated May 26, 2009

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