Human-induced climate change made Belgium’s June 2026 heatwave nearly 4°C hotter and more than doubled its death toll, according to a rapid attribution study published by researchers at Vrije Universiteit Brussel. The extreme event caused an estimated 1,181 deaths, with 665 fatalities directly linked to anthropogenic warming.
Uccle Heatwave Strains Emergency Services and Geriatric Wards
During the twelve-day heatwave spanning 17 to 28 June 2026, maximum temperatures at Uccle reached 35.5°C on 26 June. On the night of 24 to 25 June, the temperature did not drop below 24.1°C, marking the highest overnight minimum ever recorded during a Belgian heatwave since records began in 1892.
The extreme conditions pushed emergency infrastructure to its limits. On 26 June, calls to the 112 emergency number reached nearly double their usual daily volume, while geriatric wards operated at maximum capacity. Provisional figures indicate that 27 June ranked as the second deadliest day of the 21st century in Belgium.
Vrije Universiteit Brussel Analysis on Anthropogenic Warming
Researchers from the Department of Water and Climate at Vrije Universiteit Brussel published a rapid attribution report examining the mortality figures. The study estimates that heat-related deaths accounted for about a quarter of all deaths recorded during the twelve-day period. Of the 1,181 total heat-related fatalities, 665 — or 56 percent — would not have occurred without human-induced climate change.
Without anthropogenic warming, the average daily maximum temperature on the hottest day of the event (26 June) would have reached 32.1°C instead of the observed 36.0°C. The study notes that Europe has warmed at roughly twice the global average rate since the 1980s, and heat extremes in Western Europe have intensified even faster due to declining air pollution and shifting atmospheric circulation.
Our research shows that without human-induced climate change, the June 2026 heatwave would have been nearly 4°C cooler. Of the almost 1,200 deaths we link to heat, more than half would not have occurred without this extra warming. This means that global warming is already costing lives in Belgium today. That is why every fraction of a degree of warming we avoid will save lives.
Maxim Sleypen, Lead Author and researcher at VUB
Demographic and Regional Vulnerability Across Belgium
The mortality burden fell disproportionately across specific populations and regions. Women accounted for more heat-related deaths than men, and individuals aged 85 and older represented half of all heat-related fatalities.
Wallonia bore the heaviest regional toll, with Liège recording the highest provincial mortality rate attributable to climate change at 9 to 11 deaths per 100,000 inhabitants. Hainaut and Namur followed with 7 to 9 deaths per 100,000 inhabitants, as temperature anomalies in parts of southern Belgium exceeded normal ranges by 9.5 to 10°C.
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 beyond temperature alone, pre-existing health conditions coupled to socio-economic factors (housing with poor insulation, limited cooling capacity and many others). Understanding these inequalities is essential if we are to protect the most vulnerable.
Emma Kuijt, Co-Author and researcher at VUB and UCLouvain
Scientific Peer Review Status
Researchers note that the rapid attribution report relies on established methods combining epidemiological models with extreme event attribution techniques.
Three compounding factors made this heatwave so deadly: Europe is warming twice as fast as the global average, heat extremes are intensifying even faster, and the risk of death rises steeply once temperatures pass a critical threshold. Every additional increment of global warming will push more heatwaves into that lethal range. Urgent cuts to fossil fuel emissions are not optional – they are a matter of life and death.
Wim Thiery, VUB