Risk of 451,000 excess deaths over the next six months due to ‘extraordinary’ heat.

An unusually powerful El Niño could drive extreme heat across large parts of the world in the coming months, potentially resulting in around 451,000 additional heat-related deaths between September 2026 and February 2027, according to climate researchers. The figure is a projection rather than a count of confirmed deaths, based on temperature forecasts and historical links between extreme heat and mortality.

The projection was developed by researchers associated with the Climate Impact Lab at the University of Chicago. Their analysis examines how the additional warming associated with El Niño could affect mortality in different parts of the world.

Researchers say the threat is particularly serious because global temperatures have already risen as a result of human-driven climate change. The additional heat linked to a strong El Niño could further increase health risks, especially in regions that are already hot and have limited resources to cope with extreme temperatures.

Nigeria, Indonesia, Sudan, India and Brazil are among the countries expected to experience some of the highest numbers of additional heat-related deaths over the next six months. The Sahel region of Africa and parts of Southeast Asia are also projected to face significant impacts. In the United States, researchers estimate about 3,500 additional heat-related deaths during the period.

India is also expected to face a substantial impact. A separate report based on the study estimates around 15,800 additional heat-related deaths in the country over the next six months, with a significant share potentially occurring between December and February.

The consequences of El Niño could extend beyond extreme temperatures. Researchers warn that the weather phenomenon can also contribute to droughts, wildfires, flooding and water shortages, creating additional pressure on public health systems, food supplies and livelihoods.

Experts say early preparation could reduce the potential loss of life. Measures highlighted by researchers include improved heat-warning systems, cooling centres, additional medical staff during periods of extreme heat and stronger protections for people working outdoors.

The projections were developed using peer-reviewed methods that examine the month-by-month relationship between temperature and heat-related mortality across 24,378 regions worldwide. Researchers combined historical mortality patterns from 1996 to 2025 with forecasts for higher temperatures associated with the current El Niño event.

Scientists have described the current episode as an indication of what future climate conditions could look like. The extreme temperatures associated with the event are approaching levels that climate projections suggest could become more common in the coming decades as global warming continues.

Researchers stress that the projected death toll should not be interpreted as a certainty. Instead, the estimate highlights areas where timely public-health measures could potentially prevent thousands of deaths. Long-term investment in heat preparedness, resilient infrastructure and protection for vulnerable populations will also be important as extreme heat becomes more frequent.

The health impacts may continue beyond February 2027 in some regions, with elevated heat-related mortality potentially lasting into the middle of next year even if the El Niño event itself weakens.