WORLD WEATHER ATTRIBUTION
Central Canada wildfires
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| Wildfires in Manitoba, 2021. GOES imagery: CSU/CIRA & NOAA |
Dr Friederike Otto, Senior Lecturer in Climate Science at Imperial College London, said:
“The deadly blazes in the central provinces mark a concerning start to the Canada wildfires season.
“They come after weeks of relentless heat with temperatures well above the long-term average – a clear indicator of climate change.
“If countries continue to rely on fossil fuels, the climate will keep warming, and we'll see more and more extreme heat making forests more prone to wildfires in dry years and seasons.”
Dr Clair Barnes, World Weather Attribution Researcher at the Centre for Environmental Policy, Imperial College London, said:
“There is lots of evidence linking increasing temperatures with increased wildfire risk around the world.
“More intense heat means there is a heightened risk of wildfires starting and spreading – particularly after periods of low rainfall – because higher temperatures cause more moisture to evaporate, leaving leaf litter and other fuel very dry and flammable.
“We know that Canada is getting warmer as a result of climate change, so it’s very likely that climate change is contributing to the current fire-prone conditions.”
Theo Keeping, Wildfire Researcher at the Leverhulme Centre for Wildfires, Imperial College London, said:
“Dry winters followed by hot springs create a worst-case scenario for wildfires in Canada.
“Parts of Manitoba have recorded less than half the rainfall that would be expected by this time of year and May temperatures have been more than 10°C above average.
“It's too soon to say if the central provinces could experience a record-breaking season. However, ongoing hot and dry weather is expected, which will increase wildfire risk.”
Background
Since May 11, 2025, large wildfires have been burning across several Canadian provinces, including British Columbia, Alberta, Saskatchewan, Manitoba, and Ontario.
At least 1,000 people have been forced to evacuate their homes and so far, two fatalities have been reported in Manitoba. Emergency services are working around the clock to contain the fires and support affected communities. At the time of writing, approximately 9 million people across Canada and neighboring U.S. states are under fire warnings.
The fires were fueled by strong winds and unseasonably high temperatures. Between May 11 and 13, Winnipeg saw three consecutive days with temperatures above 30°C, reaching a maximum of 36.4°C - well above the average May temperature of about 19°C. (CHNV & CBC, 2025). Large regions of southern and central Manitoba also saw temperatures above 30°C and Environment Canada issued a heat warning to alert those vulnerable to high temperatures (Winnipeg Sun, 2025).
The fires follow an unusually dry spring across much of Western and Central Canada, with several regions experiencing abnormally dry up to extreme drought conditions (Canadian Drought Monitor, 2025).
Officials at both the provincial and federal levels are coordinating firefighting efforts and disaster response measures, while environmental experts warn that the situation may worsen and Western Canada could experience a devastating fire season which usually runs from May to September (CNN, 2025). Intense fire-prone weather conditions are expected over the next week.
In contrast to Canada’s record-breaking wildfire season in 2023, when fire-weather conditions across the country reached unprecedented levels, the current 2025 fire season presents a different kind of threat. In 2023, vast areas of forest were burned during that season as nearly all components of the Canadian Fire Weather Index—except for the Initial Spread Index, which ranked third since 1950—set record highs when averaged across the country.
By contrast, while the 2025 wildfires are affecting densely forested areas in Saskatchewan, Manitoba and Ontario, many fires also occurred in prairies agricultural zones.These fires are at greater risk of affecting transitional landscapes known as the wildland-urban interface (WUI) — where human development meets wildland vegetation. The WUI is particularly vulnerable to wildfire, as people and property are most exposed to flammable natural fuels in these areas. This shift in geography and fire behavior may help explain why, despite fewer fires burning in forested regions, the 2025 season has already resulted in two fatalities—both in Manitoba—whereas no deaths were recorded during the 2023 season.
Attribution analysis of 2023 Canada wildfires
Wildfires are complex natural phenomena influenced not only by climate but also by vegetation, land cover, and human activities. As a result, isolating and quantifying the specific contribution of climate change to observed wildfire outcomes—such as burned area or the number of fire events—is challenging. For this reason, many scientific studies focus instead on the weather conditions that are conducive to wildfires, rather than the fires themselves.
In this context, the World Weather Attribution (WWA) team conducted an attribution study of the 2023 wildfires in Quebec, using the Canadian Fire Weather Index fire danger rating system. To capture both the intensity and the duration of extreme fire weather conditions across the region, the study focused specifically on the Cumulative Daily Severity Rating (DSR). This index reflects how difficult it is to suppress fires, and is appropriate for averaging over multiple days and relatively homogenous areas. Higher values indicating more severe fire weather and a greater likelihood of sustained, intense fire activity.
By integrating multiple lines of evidence—including syntheses of past climate data, historical and future model projections, and established physical understanding—the WWA study concluded that the cumulative DSRexperienced between January and July 2023 in Quebec was at least seven times more likely to occur due to human-induced climate change. Furthermore, the severity of this index was approximately 50% higher than it would have been in a pre-industrial climate. These quantitative findings are specific to the Quebec study region and the extreme fire weather event observed in May–June 2023. Of the hot, dry and windy weather conditions that factor into the DSR, the study found that warm spring temperatures were a key driver.
The influence of climate change on the Western Canada wildfires
The DSR was developed to assess fire risk in forested areas, and thus may be less suitable for agricultural landscapes. Nevertheless, as shown in Figure 1, cumulative DSR values have been increasing across Canada, albeit with regional variations in the magnitude of trends.
Importantly however, the 2023 study identified rising temperatures as the primary driver behind increasing fire-weather risk—a conclusion that can be extended to 2025 . While the specific characteristics of this year's fire season differ, the underlying influence of climate change remains. We can state that anthropogenic climate change has increased the likelihood and severity of high fire-weather conditions in Canada.
Figure 1: Map of relative change in intensity in annual accumulated DSR associated with 1.3°C of global warming (ERA5, using data from 1950-2023). Black dots mark active fires in May 2025, identified with high confidence (>80%) in the MCD14DL MODIS Active Fire and Thermal Anomalies product.
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