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Climate change doubled the number of heat-related deaths in Belgium during the heatwave of June 2026
New study links 665 deaths directly to man-made global warming during the deadliest heatwave ever recorded in Belgium
A new rapid attribution study by the Vrije Universiteit Brussel (VUB) shows that human-induced climate change made the June 2026 heatwave in Belgium 3.9 °C warmer and more than doubled the number of heat-related deaths. Of the estimated 1,181 deaths statistically linked to the extreme temperatures between 17 and 28 June 2026, 665 – or 56 per cent – would not have occurred without anthropogenic climate change. This is the first time that heat-related deaths during a specific Belgian heatwave have been attributed to human-induced climate change.
The heatwave of June 2026 was the deadliest ever recorded in Belgium. During the twelve days it lasted, maximum temperatures in Uccle peaked at 35.5 °C on 26 June. On the night of 24 to 25 June, the temperature did not fall below 24.1 °C – the highest night-time minimum temperature ever recorded during a Belgian heatwave since records began in 1892. The emergency services were overwhelmed: on 26 June, the number of calls to the 112 emergency number was almost double the usual figure, and geriatric wards were operating at maximum capacity. According to provisional figures, 27 June was the second deadliest day of the 21st century in Belgium.
The study, published today as a rapid attribution report by researchers from the Department of Water and Climate at the VUB, is the first attribution of heat-related deaths to human-induced climate change for a specific Belgian heatwave. It uses established, peer-reviewed methods that combine epidemiological models – which link daily maximum temperatures to the risk of mortality – with methods for attributing extreme events, which estimate how much warmer the heatwave became as a result of human-induced climate change. This rapid attribution study demonstrates that the health risks of climate change are already a reality today and that fossil fuel emissions have cost the lives of hundreds of Belgian citizens this June alone.
- Climate change made the heatwave 3.9 °C warmer. Human-induced climate change made the 12-day peak period 3.9 °C warmer than it would have been in a world without anthropogenic warming. On the hottest day (26 June), for example, the average daily maximum temperature in Belgium would have reached 32.1 °C without climate change, rather than the observed 36.0 °C.
- Climate change has more than doubled the number of heat-related deaths. The study estimates the number of heat-related deaths during the heatwave at 1,181. Heat-related deaths thus account for around a quarter of all deaths recorded during the heatwave. Of these heat-related deaths, 665 (56 per cent) are attributable to human-induced climate change.
- Women and the elderly bear the heaviest burden. There are more heat-related deaths among women than among men. People aged 85 and over account for half of all heat-related deaths (heat with or without climate change).
- Wallonia – and Liège in particular – was the hardest hit. The provincial mortality rate attributable to climate change was highest in Liège (9–11 deaths per 100,000 inhabitants), followed by Hainaut and Namur (7–9 deaths per 100,000 inhabitants). In parts of southern Belgium, temperature anomalies were more than 9.5 to 10 °C above normal.
- Belgium is warming faster than the global average. Since the 1980s, Europe has warmed at roughly twice the rate of the global average. Heat extremes in Western Europe have intensified even more rapidly, due to declining air pollution and changes in global atmospheric circulation linked to climate change. This intensification has pushed temperatures from the low-risk zone into the high-risk zone on the temperature–mortality curve, which explains the sharp rise in heat-related deaths.
Extreme heat disrupts the normal functioning of the human body, exacerbates existing conditions and can lead to serious complications such as heatstroke, dehydration and organ failure. Climate change is making dangerous heatwaves more frequent and intense, mainly due to the burning of fossil fuels such as oil, coal and gas.
Maxim Sleypen, lead author and researcher at the VUB:
“Our research shows that, without human-induced climate change, the heatwave of June 2026 would have been nearly 4 °C cooler. Of the nearly 1,200 deaths we attribute to the heat, more than half would not have occurred without this additional warming. This means that global warming is already costing lives in Belgium today. That is why every fraction of a degree of warming that we avoid will save lives.”
Emma Kuijt, co-author and researcher at the VUB and UCLouvain:
“The burden of this heatwave was not shared equally. Older people, women and communities in the most deprived areas suffered the most – likely exacerbated by factors going beyond temperature alone: pre-existing health conditions combined with socio-economic factors (poorly insulated homes, limited cooling capacity and many others). Understanding these inequalities is essential if we are to protect the most vulnerable.”
Wim Thiery, senior author and professor at the VUB:
“Three mutually reinforcing factors made this heatwave so deadly: Europe is warming twice as fast as the global average, heat extremes are becoming more intense even faster, and the risk of death rises sharply once temperatures exceed a critical threshold. Every further step in global warming will push more heatwaves into that lethal range. Urgent reductions in fossil fuel emissions are not an option – they are a matter of life and death.”
The findings come at a crucial moment. The summer of 2026 was the hottest ever recorded in Belgium, with three official heatwaves. The June heatwave alone was identifiedby World Weather Attribution as part of a wider European heatwave that would have been virtually impossible in a pre-industrial climate. As global temperatures continue to rise, such events will become more frequent, more intense and deadlier – unless mitigation efforts are stepped up.
The authors call on policymakers to keep global warming in line with the Paris Agreement, to significantly increase investment in adaptation – including heat action plans, early warning systems and strengthened public health infrastructure – and to ensure that the most vulnerable communities are protected from the growing risks of extreme heat. Every degree of warming that is avoided means lives saved.
Follow this link to access a full press pack containing: the press release in other languages, the rapid attribution report and the image from the press release as a PNG file. |
Note to editors:
- This rapid attribution report has not yet been peer-reviewed. It uses established, peer-reviewed methods, but the results may still change slightly. Version 1 was published on 16 October 2026 and will be submitted for peer review.
- Heat-related deaths are deaths statistically associated with heat, on days when the daily maximum temperature exceeds the Minimum Mortality Temperature (MMT) – the temperature at which the risk of mortality is lowest. In Belgium, MMTs range between 20.5 °C and 21.5 °C, depending on gender and age group.
- Deaths attributable to climate change are calculated as the difference between the number of heat-related deaths at observed temperatures and the number of heat-related deaths at counterfactual temperatures (i.e. the temperatures that would have occurred without human-induced climate change).
- Proportion of heat-related deaths attributable to climate change: deaths attributable to climate change, divided by the total number of heat-related deaths.
- Provincial mortality rate attributable to climate change: number of heat-related deaths attributable to climate change per 100,000 inhabitants of a province.
- Heat-related deaths were calculated using heat-mortality relationships at provincial level; the totals are higher when heat-mortality relationships at district or city level are used.
- The study’s findings support the excess mortality figures independently reported by Sciensano, the Belgian National Institute for Public Health, which recorded 2,018 excess deaths during and immediately after the heatwave – the highest number of any Belgian heatwave since monitoring began in 2003. We note that excess mortality and heat-related deaths are different concepts calculated using different methods (further information is provided in the study).
- The study was carried out by researchers from the Department of Water and Climate (HYDR) at the Vrije Universiteit Brussel, in collaboration with colleagues from UCLouvain, the Royal Meteorological Institute of Belgium (KMI) and KU Leuven.
Contact:
- Lead author: Maxim Sleypen, Department of Water and Climate, Vrije Universiteit Brussel; maxim.sleypen@vub.be, +32 492 96 98 64 (WhatsApp only)
- Co-author: Emma Kuijt, Department of Water and Climate, Vrije Universiteit Brussel; Emmanuelle.Kuijt@vub.be, +32 484 89 80 64
- Co-author: Rosa Pietroiusti, Department of Water and Climate, Vrije Universiteit Brussel; rosa.pietroiusti@vub.be, +32 496 83 66 63
- Senior author: Prof. Dr Wim Thiery, Department of Water and Climate, Vrije Universiteit Brussel; wim.thiery@vub.be, +32 2 629 30 29
- Policy Impact Lead: Dr Marie Cavitte, Department of Water and Climate, Vrije Universiteit Brussel; marie.cavitte@vub.be, +32 470 19 24 15
Koen Stein
