The conditions underlying intense July wildfires in Ontario and Northwest Territories were made roughly twice as likely due to human-induced climate change, said a new report published Thursday.
The report by an international team of scientists says what were once rare fire conditions are now increasingly likely today due to climate change, driven by the burning of fossil fuels.
“The geographic spread of these fires is scary and shows that despite preparedness from wildfire governance, adaptation alone is not enough,” said Theodore Keeping, a co-author and Imperial College London research associate.
“We need to rapidly move away from fossil fuels to avoid events like this becoming even more of a reality.”
The World Weather Attribution report says early observations indicate the hot, dry and windy conditions fuelling fires in Northwest Territories could now be expected to occur every two to six years, and every six to 15 years in Ontario.
In a world without human-caused climate change, the report suggests those conditions would have been much rarer, or less than once in 40 years.
Early estimates suggest this is the worst wildfire season on record in Ontario and in Northwest Territories’ top 10, as measured by area burned.
The study garnered the attention of the United Nations climate chief, who said the science backed up “what the people on the front lines already know.”
“Humanity’s addiction to burning massive amounts of coal, oil and gas is heating our planet, turning more of Canada’s vast forests into tinderboxes, and spreading dangerous smoke far beyond the flames,” said Simon Stiell, the UN Climate Change Executive Secretary.
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The vast majority of Ontario’s wildfires burned during a few intense days in July, on the back of a scorching heat wave and intense lightning activity along a roughly 500-kilometre storm front over the province’s northern boreal forest.
Thousands of evacuees from more than a dozen mostly First Nations communities fled their homes while noxious plumes of smoke deteriorated air quality for millions of people from Thunder Bay to the northeastern United States.
Extreme fire weather has been more sustained in Northwest Territories, where fires have remained active and spread over a long period rather than being driven by a single week of explosive growth.
Thursday’s report, whose co-authors included several scientists across the federal public service, highlighted the disproportionate impact of the wildfire season on First Nations and the importance of including those communities in risk assessments and preparedness plans.
Chief Russell Wesley of the Cat Lake First Nation in northwestern Ontario, one of evacuated communities, said this year’s fires were a “warning” that the province and Ottawa’s current approach is insufficient.
In a news release, Wesley called for action on 11 priorities, including the creation of a First Nations wildfire authority and the expansion of Indigenous fire stewardship programs. Indigenous burning practices, the setting of small, low-intensity fires guided by traditional knowledge, were excluded for decades by governments but have been shown to boost diverse, fire-resistant landscapes and clear the forest of dead debris that could otherwise help fuel more intense flames.
“Maintaining healthy forests is not only an environmental responsibility; it is essential to our survival as First Nations peoples,” said Wesley.
“Without healthy forests, our communities, cultures and future generations are at risk.”
To come up with the results in Thursday’s report, scientists used observations and climate models focusing on the seven-day and 30-day periods of most extreme fire weather in Ontario and Northwest Territories. They then compared those conditions against what would have been expected in a world without fossil fuel emissions.
For both periods in Ontario, those conditions were made about twice as likely due to climate change, the report found. In N.W.T., the likelihood of the most intense seven-day period was five-hold, while the 30-day period was double.
Adapting to a future with more intense wildfires could include supporting more fire-resistant tree species, strengthening early warning systems and steering new development away from high-risk areas, the report says.
But adaptation can only go so far. Fire is a natural part of the boreal ecosystem, but as climate change fuels more frequent, larger and more intense blazes, forest management becomes less effective and fires become harder to control, the report says.
Canada has seen three consecutive intense fire seasons, going back to the record-breaking 2023 season. The same group behind Thursday’s report published a similar analysis of Quebec’s season that year, finding it was made seven times more likely due to climate change.
“This time, we studied Canada, for the second time in three years. Less than a week ago, we looked at France and Spain. A few months ago, we were looking at Chile and Argentina,” said co-author Friederike Otto, climate science professor at Imperial College London and co-founder of World Weather Attribution.
“What is going to be next?”
© 2026 The Canadian Press