Extreme Heat

Heat advisories and warnings

Southwestern Public Health (SWPH) declares heat warnings when prolonged exposure to outdoor conditions could prove dangerous to public health. Environment and Climate Change Canada’s meteorological services notifies Public Health when there is an impending heat event forecast for our area.

SWPH will then issue a Heat Warning or Extended Heat Warning based on the duration and intensity of the expected conditions:

• Heat Warning – when forecast temperatures are expected to be at least 31°C and overnight temperatures are at or above 20°C for two days or the Humidex is forecasted to be at least 40°C for two days.
• Extended Heat Warning – When forecast temperatures are expected to be at least 31°C and overnight temperatures are above 20°C for three or more days or Humidex is at least 40°C for three or more days.

Heat warnings or extended heat warnings are posted on the SWPH website and social media channels, and are distributed to local media, child care providers and other community partners. Learn more about heat alert guidelines for child care centres.

Protecting yourself in hot weather

A combination of high heat and high humidity can be dangerous. Anyone who experiences physical distress because of extreme temperatures should seek medical attention immediately, either by calling 911 or by going to the nearest emergency department. 

• Drink plenty of water before feeling thirsty and avoid alcoholic and caffeinated beverages
• Limit time outdoors when the UV Index (ultraviolet ray strength) is most intense, between 11am - 4pm
• Apply Sunscreen with SPF 30 (or higher) 20-30 minutes before going outside to ensure absorption - Re-apply every 2-3 hours
• Wear a hat and light, loose-fitted clothing
• Avoid heavy physical activity outdoors
• Seek shade at a park or greenspace or use an umbrella
• Cool off in an air-conditioned space when available
• Use a fan - you can place a bowl of cold water or ice in front of an electric fan to create a cool breeze
• Take a cool bath or shower
• Keep your home cool
  • Close window shades during the hottest part of the day to reduce direct sun exposure
  • Avoid cooking during the hottest period or the day
  • Unplug large electronics such as televisions that produce heat
• NEVER leave children or pets in a vehicle
• Visit one of the cooling centres listed below
• Learn more tips for staying cool without air conditioning

Cooling Centres

Centres like libraries, arenas, and other public buildings are great places for the public to seek relief from the heat. These locations typically include air conditioning, seating and water and are managed by each city, town or township. When a heat warning is issued, these locations can be designated as cooling centres and hours extended if there is a community need. Contact your local municipality for more information.

Heat related illnesses

Heat alert guidelines for child care centres

SWPH strongly urges child care centres to develop extreme weather policies and plans to protect the safety and well-being of the children in your care. Find ways to protect yourself and children during hot weather and know the signs of heat related illness. Be a role model by practicing sun and heat safety behaviour for children to see. 

Get more information

Learn about public weather warnings and visit the following websites for more information:

• Health Canada: Keep Children Cool! Protect Your Child From Extreme Heat
• Health Canada: You’re Active in the Heat. You’re at Risk! Protect Yourself From Extreme Heat
• Health Canada: It’s Way Too Hot! Protect Yourself From Extreme Heat
• Ontario Ministry of Labour: Heat Stress
• Health Canada: UV Index and Sun Safety