A rapid scientific analysis published on Wednesday estimates that approximately 2,300 people died across a dozen European cities during the extreme heatwave that swept Western Europe in late June and early July.
Researchers attribute around 1,500 of these deaths directly to climate change, which they say exacerbated the severity of the event.
The study, conducted by scientists from Imperial College London and the London School of Hygiene and Tropical Medicine, focused on the ten-day period ending 2 July, when parts of Spain recorded temperatures exceeding 40°C and wildfires erupted in France.
Using peer-reviewed methods and established epidemiological models, the researchers calculated heat-related mortality across 12 cities, including Madrid, Barcelona, Milan, and London. They concluded that climate change had raised heatwave temperatures in these areas by as much as 4°C, significantly increasing health risks to vulnerable populations.
“Climate change has made it significantly hotter than it would have been, which in turn makes it a lot more dangerous,” said Dr Ben Clarke, a researcher involved in the study at Imperial College. The analysis accounted for deaths where heat was the underlying cause, either directly or by aggravating existing medical conditions.
The scientists noted that most heat-related deaths are not officially reported and that several European governments do not release real-time mortality data. As such, they used historical records and statistical models to generate their estimate.
The findings arrive as the European Union’s Copernicus Climate Change Service confirmed that June 2025 was the hottest June ever recorded in Western Europe. The month ranked as the third-hottest globally, following June 2024 and June 2023. According to Copernicus, much of the region experienced “very strong heat stress”, where temperatures felt like 38°C or higher.
“In a warming world, heatwaves are likely to become more frequent, more intense and impact more people across Europe,” said Samantha Burgess, Deputy Director at Copernicus. The service attributed the pattern to a combination of persistent high-pressure systems and elevated baseline temperatures linked to greenhouse gas concentrations.
The analysis follows warnings issued in previous years regarding Europe’s vulnerability to rising temperatures. In 2023, researchers reported that up to 61,000 people may have died during heatwaves in 2022 alone, highlighting chronic shortcomings in national preparedness and emergency response systems.
The current findings renew questions about whether European countries are adequately adapting to the growing threat of extreme heat. Public health experts argue that measures such as early warning systems, targeted outreach to at-risk groups, and urban design modifications—including increased shade and access to cooling centres—remain underdeveloped in many areas.
The ongoing increase in average global temperatures is largely driven by the accumulation of greenhouse gases from fossil fuel combustion. This has led to more frequent instances where ambient temperatures surpass thresholds considered dangerous for human health. While heatwaves are a recurring natural phenomenon, scientists stress that their intensity and duration are now strongly amplified by anthropogenic climate change.
Photos from the recent heatwave show residents in cities such as Skopje resorting to handheld fans and makeshift shade in an effort to stay cool, while emergency services in parts of Spain and southern France were deployed to contain fast-moving wildfires.
The authors of the study acknowledge the provisional nature of their estimates, but argue that rapid analyses are vital in highlighting the immediate impacts of extreme heat and prompting necessary policy responses. With Europe’s ageing population and increasingly urbanised environment, experts warn that the continent faces heightened risks unless climate mitigation and adaptation strategies are accelerated.
Although the data remains preliminary, the consistency with past mortality trends underscores a growing consensus: without significant reductions in greenhouse gas emissions and improved public health measures, heatwaves will remain one of the most lethal consequences of climate change in Europe.
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