Extreme heat events are becoming more frequent across Ontario as the climate changes. CAA North & East Ontario tracks these trends and provides safety guidance to help residents, drivers and families stay protected when temperatures rise above seasonal norms.
Understand the health risks, prepare your household and protect vulnerable individuals—including children, seniors and pets.
What is a heat wave?
Extreme heat events, or “heat waves” are a series of days where the temperature greatly exceeds the average for that location, reaching heat warning thresholds. Unlike the humid Ontario days in June, July and August, when the climate is hot but normal, heat waves are linked to climate change.
Health risks of extreme heat
Heat-related illness can affect anyone. Mild heat illnesses include heat cramps and heat rash. Heat exhaustion is more severe, with symptoms like sweating, dizziness, headache, rapid breathing, extreme thirst and nausea.
Heat stroke, on the other hand, is a medical emergency. Symptoms include high body temperature, confusion, lack of coordination, dizziness, and fainting. The person may also stop sweating and have very hot skin.
Call 911 if you suspect heat stroke.
Who is most at risk
Infants, older adults, and pregnant individuals are at risk of heat-related illness. Those with chronic conditions or illnesses, such as heart disease, diabetes, or respiratory issues, as well as people on certain medications, may be more sensitive to heat.
Anyone working outdoors or living in homes without air conditioning is also more exposed to weather conditions. Know who is most vulnerable in your community and regularly check on neighbours, friends or family members who may need extra support.
Indoors
Focus your energy-efficiency efforts on a small number of rooms in your home. Run your air conditioner if you have one and circulate air using fans and cross-ventilation.
Reduce indoor heat by limiting the use of heat-generating appliances, keeping blinds closed to block sunlight, and closing windows when the outdoor temperature is higher than the indoor temperature.
Outdoors
Time spent outside should be limited as much as possible during extreme heat. Stick to shady areas and reschedule outdoor events where possible.
Be mindful of urban heat islands — areas in cities and towns where buildings, parking lots, and dark surfaces absorb and radiate heat, making them more dangerous during heat events. Hot concrete and asphalt can reach temperatures high enough to burn paws. If the pavement is too hot for your hand, it is likely too hot for your pet.
In your vehicle
Never leave a child or pet unattended in a parked vehicle during extreme heat. Interior temperatures can climb to life‑threatening levels within minutes, even when outdoor temperatures feel moderate.
Simple habits can prevent accidental entrapment. Get in the routine of checking the back seat every time you exit your vehicle. You can also use visual cues, such as placing your phone or bag in the rear seat, to ensure you always look before locking the doors.
Protecting your pets
Pets face serious health risks during extreme heat events. When combined with humidity, extreme heat reduces an animal's ability to cool down. To protect your pets:
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Limit exercise on very hot days.
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Never leave pets unattended in a hot backyard or vehicle.
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Provide shade and fresh water at all times.
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Use ice packs or cold damp towels on their head, neck, and chest to cool them down quickly.
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Watch for signs of heat stroke, such as excessive panting, drooling, or collapse, in dogs.
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If your cat is panting, this is an emergency sign. Immediately move them to a cool area and contact a veterinarian.
Prepare before a heat warning is issued
Make sure you and your family are ready
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Know how heat warnings are issued in your area and sign up for municipal emergency notifications if needed.
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Before a heat wave, ensure your air conditioner and fans are functional and serviced.
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Look into cooling centres in your area, like libraries, community centres, beaches, pools and splash pads.
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Put together an emergency kit that includes backup power options, such as batteries and power banks, in case of power outages.
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Keep cold packs, a flashlight, a battery‑operated fan and radio, and non‑perishable food on hand.
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Reach out to elderly or at‑risk neighbours before and during heat events.
Additional resources
FAQ
An extreme heat event (commonly known as a “heat wave”) occurs when temperatures exceed 29°C on two or more consecutive days with no overnight relief. In Northern and Eastern Ontario, these events are becoming more frequent due to climate change. Environment Canada issues heat warnings when dangerous conditions are forecast for a region.
Extreme heat can cause dehydration, heat cramps, heat exhaustion, and heat stroke. Hot weather impacts some groups more than others. Infants, older adults, and pregnant individuals may be more sensitive to heat or have a decreased ability to regulate their own temperature. Heat stroke is a medical emergency: if someone shows signs such as confusion, very high body temperature, or loss of consciousness, call 911 immediately.
Always keep your pet’s water bowl filled and accessible. Prioritize hydration with cool water and avoid outdoor activities during peak heat hours (typically 11 a.m. to 3 p.m.). Make sure to give your child plenty of water before they feel thirsty. If you’re leaving home, always carry a reusable water bottle to stay hydrated.
Yes. Interior vehicle temperatures can rise to life-threatening levels within minutes of parking, even on a mild day in direct sunlight. Always prioritize safety by never leaving vulnerable passengers unattended, even if you are just stepping away for a moment.
During heat warnings, many municipalities in the CAA North & East Ontario territory open public cooling centres. Visit 211 Ontario or contact your local public health unitto find resources available near you. During periods of extreme heat, Ottawa, Sudbury, and other major centres typically post updates on their social media channels.
