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Pearson Airport registered 24 very hot days above 30 C, 10 days more than historical norms. In the 1980s, ‘90s and 2000s, there was an average of 14 very hot days a summer. Another six days this summer fell just a few fractions of a degree shy of the 30 C mark.

Extremely hot days above 35 C used to be rare — É«É«À² didn’t always get one a summer. This year, the city suffered through five.

The pattern held across the region. Hamilton, Ottawa and Windsor sweltered too, and Barrie actually out-baked É«É«À², with three extra very hot days.

“Wherever you looked across southern Ontario, it was hot,” Phillips said.

Summer 2025 was not the hottest summer on record, Phillips added. Five recent summers had higher average temperatures. But its extreme heat was concentrated in a tighter-than-normal window of time, making the heat hard to escape.

This summer also offers an unwelcome hint at what the future might hold, Phillips said. Climate models show that the number of hot and superhot days É«É«À² experienced this summer is in line with what climate models predict the city will experience as the Earth warms because of humans burning fossil fuels.

“In many ways, it was kind of almost a preview, a dress rehearsal, of what we’ll experience as normal in 2050,” Phillips said, though those numbers could decrease dramatically by the end of the century in scenarios where the world sharply curtails its greenhouse gas emissions.

Phillips emphasized the human toll of extreme heat, noting that there were double the average number of “tropical nights,” when the minimum temperature never falls below 20 C. Hot nights can be especially dangerous, since the body never gets a chance to cool off.

A new analysis of heat deaths in European cities, published Wednesday by researchers at Imperial College and the London School of Hygiene and Tropical Medicine in the U.K., indicates the enormous toll that climate change is exacting on human health.

Epidemiologists estimated that of the 24,400 estimated heat deaths this summer across more than 850 European cities, two-thirds were due to temperatures that have intensified because of human-induced warming. In other words, an extra 16,500 heat deaths occurred this past summer compared to a summer that did not experience extra heating from human activities. 

The epidemiologists who released the analysis, which has not been peer-reviewed, said it was likely an undercount, since the estimate only looked at about 30 per cent of Europe’s population. 

Deaths aren’t the only risk: A Star investigation recently showed that workplace injuries spike on the hottest days of the year. 

Ontario’s coroner does not track heat-related deaths, though doctors, lawyers, and advocacy groups for seniors have asked the province repeatedly to start collecting this information, arguing it would help protect the most vulnerable from a rapidly growing threat.