Last week, temperatures in Toronto hit 36 degrees Celsius, and the humidex climbed to 48. For almost 40 people, that Toronto heat wave was enough to land them in an emergency room.
What Happened During Toronto's Heat Wave Last Week?
Toronto Public Health confirmed 39 heat-related ER visits at Toronto hospitals between June 30 and July 4, during an Environment Canada orange-level heat alert. The worst single day was July 2, with 15 people arriving at emergency departments with heat-related illness at the peak of the wave.
Dr. Edward Xie, an emergency physician at the University Health Network, said his ER was busier than usual, though not every visit can be cleanly categorized as heat-caused, since extreme heat often worsens existing conditions rather than causing illness from scratch. "Anecdotally, yes, absolutely I would say that the number of patients coming in has been higher than usual during this past week," he told CBC News. Toronto Public Health noted that heat-related ER visits don't capture the full picture either, since heat quietly worsens cardiac and respiratory conditions and many people affected never reach a hospital at all.
Why Is This Heat Wave Warning a Bigger Deal Than Usual?
This is the second significant Toronto heat wave in just over a month. In June 2025, 42 people ended up in emergency rooms over a three-day heat wave. Last week's warning lasted five days, longer than the one before it, part of why these visits keep climbing year over year.
Climate change is increasing both the severity and duration of heat waves. Dr. Xie put it plainly: relying on individual preparedness, or even air conditioning, isn't a long-term fix. "We can't air condition our way out of this root problem, and relying on air conditioning puts us one power outage away from disaster," he said. The federal government's guide to heat-related illness has more on how Canada tracks these events. The heat is here now and it will be back, so what you do during the next heat wave warning matters more than what happened during this one.
Which Heat Exhaustion Warning Signs Should You Watch For?
Dr. Xie recommends treating a heat warning the same way you would any other emergency: prepare before it peaks, act during it, and know when to get help. Drink cool fluids steadily throughout the day, not just when you feel thirsty, and avoid alcohol and sugary or caffeinated drinks. A fan alone can end up recirculating hot air once it's this extreme. A wet cloth on the neck, a cool shower, or getting into an air-conditioned space like a library or shopping centre will do far more, and Toronto's cooling centre finder can point you to the nearest one.
Check on the people around you, too. Older adults, people with chronic conditions, outdoor workers, and anyone without air conditioning are at the highest risk. The heat exhaustion warning signs include heavy sweating, weakness, a fast but weak pulse, nausea, and pale or clammy skin. Heat stroke is more serious: sweating stops, temperature climbs above 40 degrees, and the person may become confused or lose consciousness, a 911 situation.
Got Questions About This Toronto Heat Wave?
What's the difference between heat exhaustion and heat stroke?
Heat exhaustion causes heavy sweating, weakness, and nausea, but the person stays coherent, and those heat exhaustion warning signs are your cue to cool down fast. Heat stroke is more severe: sweating stops, skin can turn hot and dry, and the person may become confused. That needs 911, not a wait-and-see approach.
How many people were affected by Toronto's heat wave?
Toronto Public Health recorded 39 heat-related ER visits during last week's Toronto heat wave, with 15 on the worst single day, July 2, not counting people whose symptoms worsened at home.
What should I do if I don't have air conditioning during a heat warning?
Head to a cool public space like a library, community centre, or shopping mall. A cool shower and a wet cloth on the neck help too, since a fan alone isn't enough once it's this extreme.
Heat waves are no longer rare outliers in Canada, and knowing when symptoms cross into emergency territory is genuinely useful information to have. If you're not sure whether your symptoms need medical attention, a walk-in clinic or urgent care centre can help you figure that out without the wait of a busy ER. Find one near you at medimap.ca, or browse the Medimap Health Hub for more on staying safe this summer.
This article is for general information and is not medical advice, diagnosis, or treatment. If you or someone near you shows signs of heat stroke, call 911 immediately.
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