Hot Sun Sky

Extreme Weather – Heat

Last reviewed/revised: June 11, 2024

While many of us wait all year for the warm days of summer, hot temperatures can be unsafe. Extreme heat can affect everyone, but some people are at greater risk than others. This generally relates to a person’s ability to cool off or regulate their body temperature. Extreme heat can also be connected to power disruptions and poor air quality, which can impact health and other community services. 

The good news is that the negative health impacts of heat can be prevented. Review the sections below to learn about preparing for extreme heat, heat warnings, preventing heat-related illness, and knowing when to seek help. 

There are many places in our region where you can cool down, including beaches, wading pools or splash pads, and air-conditioned public spaces such as shopping centres or places of worship.  

Heat-related illnesses can be medical emergencies! Read through the sections below to learn the signs and know when to call 911. 

Heat Stroke 

Heat stroke is a medical emergency! If you or someone else has any symptoms of heat stroke, call 911. 

Signs and symptoms of heat stroke (any one of the following):  

  • Body temperature greater than 39°C (102°F) 
  • Red, hot and dry skin (but not sweating) 
  • Fainting or loss of consciousness 
  • Throbbing headache 
  • Dizziness, nausea or vomiting 
  • Difficult speaking 
  • Unusual coordination problems 
  • Rapid breathing or faint rapid heart rate 
  • Extreme thirst 
  • Unusual confusion or disorientation 
  • Dark yellow urine and decreased urine output  

While waiting for medical help, cool the person right away:   

  • Move the person to a cool place if possible 
  • Apply cold wet towels or icepacks to large areas of the skin 
  • Fan the person  

Heat Exhaustion  

Heat exhaustion is a milder form of a heat-related illness that can develop after several days of exposure to high temperatures.  

Signs and symptoms of heat exhaustion  

  • Heavy sweating 
  • Extreme thirst  
  • Skin rash 
  • Paleness 
  • Muscle cramps 
  • Tiredness 
  • Weakness 
  • Dizziness or fainting  
  • Headache 
  • Nausea or vomiting 

If heat exhaustion is untreated, it may progress to heat stroke very quickly. Call 911 if symptoms persist or get worse.   

Steps to cool the body during heat exhaustion 

  • Move to a cool place 
  • Drink nonalcoholic liquids (water is best) 
  • Rest 
  • Take a cool shower, bath, or sponge bath 
  • Wear lightweight clothing 

Consult a healthcare provider or call Health811 (TTY: 1-877-797-0007) if you are experiencing symptoms of heat-related illness. 

Heat-related illnesses (e.g., heat rash, heat stroke, heat exhaustion) can be mild or life-threatening. These illnesses are the result of a person’s body getting hotter faster than it can cool down. Heat-related illnesses are preventable – follow the tips below: 

Know Your Risk 

While extreme heat can put everyone at risk from heat illnesses, health risks from extreme heat are greatest for: 

  • Older adults 
  • Infants and young children 
  • Pregnant people 

And people:  

  • with chronic illnesses (breathing and heart conditions; mental health illnesses)  
  • taking certain medications  
  • who work, exercise, or spend time outdoors 
  • experiencing homelessness  
  • with low-income  
  • who are socially isolated or living alone  
  • with cognitive impairment, or decreased mobility 
  • who use substances  

The more risk factors a person experiences, the higher their health risks. 

Protect Yourself 

  1. Stay hydrated 
    • Drink plenty of cool liquids, especially water, before you feel thirsty.  
    • Thirst is not a good indicator of dehydration. IF you are thirsty, you are likely already dehydrated!  
  2. Stay cool 
    • Try to keep your home comfortable:  
      • Air conditioners (or heat pumps), especially for persons vulnerable to extreme heat can help keep the temperature low. 
      • Block sun out by closing awnings, curtains or blinds during the day. Placing aluminum foil-covered cardboard in a window to reflect heat back outside may be a good temporary option. 
      • Opening windows at night can help, but only if outdoor temperature is lower than the indoor temperature! Turn off heat-generating devices (electronics, appliances, lights).  
      • Prepare meals that don't need to be cooked in your oven (e.g., BBQ or a fresh salad!) 
      • Monitor the indoor temperature. For heat-vulnerable people, health risks increase at indoor temperatures over 26°C (79°F), and temperatures higher than 31°C (88°F) are considered dangerous. 
    • Take cool showers/baths until you feel refreshed.  
    • Spend time in cooler areas of your home (e.g. lower floors); sleep in the coolest room, if possible. 
    • Fans can support air flow. 
      • Placing a bowl of ice in front of the fan can help cool the air that that fan is blowing.  
      • When the indoor temperature is high (35°C or hotter), fans may give a “sense” of cooling but will not actively lower your core body temperature. Do not rely on fans as your primary cooling method during an extreme heat event. 
    • If your home is too hot, spend a few hours in a cool place.  
      • Remember, some homes will remain very hot even once the outdoor air temperature has cooled down, so it is important to keep checking the indoor air temperature.  
  3. Limit time outdoors & be prepared
    • Avoid strenuous outdoor physical activities in the heat, especially during the hottest times of the day (typically 12:00 p.m. to 4:00 p.m.).  
    • If you are outdoors: 
      • Wear loose-fitting, light-coloured clothing made of breathable fabric.  
      • Avoid sun exposure, seek shade, and practice sun safety. 
  4. Check on family, friends, and neighbours 
    • Learn how to do a health check here (NCCEH) 
    • If you have air conditioning, consider inviting vulnerable family or friends to your home. 

Know When to Get Help 

  • Pay attention to how you and those around you feel.   
  • Watch for signs of heat-related illness (see previous section). 
  • Consult a healthcare provider or call Health811 (TTY: 1-877-797-0007) if you are experiencing symptoms of heat-related illness. 

Climate change is leading to increases in average temperatures for the PPH region. The region will see a significant increase in the number of very hot days (30°C or hotter) over the next several decades. This means that heat events or “heatwaves” are also likely to become more frequent and more intense. Visit the PPH Climate Change webpage for more information on climate change.   

To prepare for increases in extreme heat in our community: 

Be Aware 

  • Stay up to date on weather forecasts and alerts. 
  • Receive alerts with Environment Canada’s WeatherCAN app 

Have a Plan 

  • Know your home’s cool spaces (e.g. basement).  
  • Ensure your cooling equipment (e.g., air conditioning, fans) is working properly.  
  • If your home gets very hot and you do not have air conditioning, make a plan to stay with family/friends who do. 
  • Consider going to public places that may be cooler, like libraries, community centres, local beaches, and splash pads. 
  • If you have family, friends or neighbours who may be at higher risk of illnesses or live alone, plan to check in on them. Learn how: Health checks during extreme heat events (NCCEH). 
  • Review Emergency Preparedness guidelines for when an extreme heat event lasts for 3 or more days or overlaps with a power outage or poor air quality. 

Consider Home Upgrades 

Peterborough Public Health uses the harmonized provincial Heat Warning and Information System to issue alerts related to extreme heat. In the Peterborough region, a Heat Warning or Extended Heat Warning is issued by Environment and Climate Change Canada based on these temperature criteria: 

  • daytime temperatures are expected to be 31°C or warmer and nighttime minimum temperatures of 20°C or warmer  


  • when Humidex values are expected to reach 40 or higher.    

A level 1 heat warning is issued when these criteria are forecast to be met for two (2) consecutive days. 

A level 2 extended heat warning is issued when these criteria are forecast to be met for three or more (3+) consecutive days. 

A level 3 heat emergency may be declared when there is an extended heat warning, combined with other risk factors like a power outage.  

Heat/Health-related Posters:  

Resources for specific populations or settings: 

See Health Canada’s website for more resources.