Human-made climate change made 10 summer heat waves more likely: experts

Environment and Climate Change Canada said several heat waves this summer were twice as likely to be due to human-made climate change, with one 10 times more likely.

Human-caused climate change made several heat waves across Canada two to 10 times more likely, Environment and Climate Change Canada said Wednesday.

The agency said summer 2025 was the 11th warmest on record and, while not “exceptional,” was warmer than the average since 1948.

“The strongest event, the most extreme event of the summer was observed in Atlantic Canada, which we found to be at least 10 times more likely because of human-induced climate change,” said Nathan Gillett, a research scientist with Environment and Climate Change Canada.

Environment and Climate Change Canada analyzed data from 17 regions of the country this summer when temperatures during a heat wave exceeded the typical hottest day of the year. For July and August, 10 met that threshold.

Nine of the hottest heat waves were seen in the Yukon, Northwest Territories, British Columbia, Alberta and Quebec, with the results showing the events were at least two — and up to 10 — times more likely due to human-made climate change than compared to the late 19th century.

Atlantic Canada saw a heat wave that was at least 10 times more likely due to human-caused climate change, specifically on Aug. 13, according to the results.

A heat wave also hit Atlantic Canada in July, with the peak daily high hitting 25.6 C.

This summer, the system showed northern Quebec saw two heat waves in July and August, where the temperatures hit 7 C or higher above the normal daily high.