Europe’s extreme summer heat killed more than 50,000 people in its cities, with climate change responsible for an estimated two-thirds of the deaths, according to research accepted for publication in Nature Health.

The findings come as a separate assessment warns that 66,800 additional heat-related deaths could occur across Sahel countries between September 2026 and February 2027 during the expected Super El Niño period.

The European study, led by researchers at Imperial College London and the London School of Hygiene & Tropical Medicine, estimated that 32,600 deaths could have been avoided if human-caused climate change had not intensified the summer heat wave.

Researchers modelled heat-related mortality across 854 European cities using historical relationships between temperatures and deaths. The study estimated that people aged 85 and older accounted for 22,500 deaths, while those aged 75 to 84 accounted for another 14,100.

Kristie Ebi, a climate epidemiologist at the University of Washington who was not involved in the study, said the findings showed that heat-related deaths remained a major public health challenge despite growing awareness of preventive measures.

“Almost all those deaths are preventable,” she said.

Africa’s heat risk

In Africa, the assessment titled 451,000 at Risk: Where Action Can Save Lives During the Super El Niño projects 66,800 additional heat-related deaths across the Sahel between September 2026 and February 2027, compared with the 1996–2025 average. Nigeria alone accounts for a projected 31,400 additional deaths during the period.

The assessment links these projections to forecast extreme heat associated with the expected Super El Niño. The figures are model-based estimates, not confirmed deaths, and should not be interpreted as deaths caused solely by El Niño.

El Niño is a natural climate pattern involving unusually warm sea surface temperatures in the central and eastern tropical Pacific Ocean. It can influence temperatures and rainfall in different parts of the world, while human-caused climate change increases the risks associated with extreme heat.

Although the European heat wave and the projected African heat impacts are not the same event, both highlight the growing threat extreme temperatures pose to public health. The European findings also show how quickly heat can become deadly, particularly for older people and other vulnerable groups.

Early action saves lives

Researchers say public health warnings, cooling centres and other preventive measures can reduce heat-related deaths. The European study’s findings reinforce the need for governments to prepare for extreme temperatures before they peak.

For Nigeria and other vulnerable countries, this means strengthening heat early warning systems, preparing health facilities, communicating safety advice and protecting outdoor workers, older people and children.

With the projected El Niño period underway, governments must act early to reduce avoidable deaths. The European experience shows that even countries with established health systems remain vulnerable when extreme heat overwhelms preventive measures.