Extreme Heat

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 who live alone
  • People experiencing homelessness

What is the Humidex?

The Humidex is a Canadian measure that describes how hot, humid weather feels to the average person. The Humidex combines the temperature and humidity into one number to reflect the perceived temperature. Because it takes into account the two most important factors that affect summer comfort, it can be a better measure of how stifling the air feels than either temperature or humidity alone.

For more information about humidity and humidex, check Warm Season Weather Hazards

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

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. Use the Health Checks During  Extreme Heat Events guide for doing in-person or remote health checks.

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 Spaces are opened.

Cooling Spaces

Cooling Spaces 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 Warming, Cooling and Clean Air Spaces 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 Alert Waterloo Region for more information on emergency preparedness.

Waterloo Region Heat, Cold and Air Quality Network

The Waterloo Region Heat, Cold and Air Quality Network, coordinated by Region of Waterloo Public Health, is a collection of local partners that work together to reduce health risks associated with extreme heat, cold and poor air quality. This network includes representatives who run the Warming, Cooling and Clean Air Spaces in Waterloo Region as well as partners who have front-line contact with vulnerable populations.

For more information, or to be added to the partnership, please contact Region of Waterloo Public Health at ExtremeHeatCold@regionofwaterloo.ca.

How to receive weather alerts from Environment and Climate Change Canada

Additional Resources

Health Canada





National Collaborating Centre for Environmental Health

Intact Centre on Climate Adaptation


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