Extreme Heat and Humidity

Staying cool is important during the summer, especially when temperatures rise above normal. Hot weather is common during summer in Waterloo Region. Exposure to heat and humidity can be hazardous to health and potentially life-threatening.

Anyone can be affected by extreme heat-related weather conditions. Risks are higher for:

  • Older adults (over the age of 65)
  • Infants and young children
  • Outdoor workers
  • People planning outdoor sports or activities
  • People with chronic illness
  • People experiencing homelessness

What is humidex?

Extreme heat and humidity are expressed as a humidex.

The humidex combines both temperature and humidity to reflect how hot it feels. The more humidity, the warmer the temperature feels.

Protect Yourself

When temperatures are warmer it takes less time to develop heat-related illnesses.

You can protect yourself from heat and humidity by:

  • Knowing the weather forecast before going outside
  • Planning ahead and modifying your plans according to the weather
  • Drinking plenty of cool liquids, especially water, before you feel thirsty (avoid drinks high in sugar, caffeine or alcohol)
  • Wearing loose-fitting, light-coloured clothing made of breathable fabric
  • Seeking shade and avoiding sun exposure
  • Taking a break from the heat by spending a few hours in a cool place
  • Taking cool showers or baths until you feel refreshed
  • Blocking the sun by closing curtains or blinds during the day
  • Preparing meals that don't require the stove

For specific guidelines for older adults, children, or being active visit Health Canada.

Exposure to extreme heat and humidity can cause:

  • Dizziness or fainting
  • Nausea or vomiting
  • Headache
  • Rapid breathing and heartbeat
  • Extreme thirst
  • Decreased urination

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

Frequently connect with vulnerable neighbours, friends and older family members, especially those who are chronically ill, to make sure they are cool and hydrated. Calling or virtual check-in is best, but if that is not possible, practice physical distancing

Heat Stroke

Heat stroke is a medical emergency. Call 911 immediately if you are caring for someone who has a high body temperature (more than 40° C), is unconscious confused or has stopped sweating.

While waiting for help, cool the person by:

  • Moving them to a cool place
  • Applying cold water to large areas of skin or clothing
  • Fanning the person as much as possible
Heat Warnings

Environment and Climate Change Canada will issue a heat warning for Waterloo Region when one or both of the following conditions is met:

  • Two consecutive days where the temperature is forecasted to be 31° C or higher during the day and 20° C or higher overnight 
  • Two consecutive days where the humidex is forecasted to be 40° C or higher

When a heat warning is issued for Waterloo Region, Public Health coordinates a community response and cooling centres are opened.

Cooling Centres
Cooling centres are buildings that are open to the public and welcome any individual inside during regular business hours to cool down during a heat warning. They include government buildings, libraries, community centres and other recreational facilities.

For more information visit the cooling centres page.

Emergency Preparedness

Emergencies can happen at any time. Be prepared with an emergency kit - it could save your life. Remember to plan ahead and listen to the weather forecast.

Find out what to include in an:

Visit Waterloo Region Emergency Management for more information on emergency preparedness.

Additional Resources

Health Canada has developed a number of new resources focused on extreme heat, many which are available in PDF or hard copy.





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