A potentially powerful El Niño event could contribute to more than 451,000 additional heat related deaths worldwide over the next six months according to estimates from scientists at the University of Chicago Climate Impact Lab.
The study reported by Inside Climate News and published on PreventionWeb on September 25, 2026 estimates that the warming associated with the current El Niño could push land temperatures about 1.2 degrees Celsius higher in some of the most affected countries between June 2026 and February 2027.
El Niño is the warm phase of a recurring Pacific Ocean climate cycle. It occurs when unusually warm ocean conditions in the central and eastern tropical Pacific influence atmospheric circulation, affecting temperatures, rainfall, storms and other weather patterns across large parts of the world.
The researchers estimate that the additional warming could produce around 44% more extremely hot days than would normally be expected. They describe the resulting conditions as resembling temperatures that climate change could otherwise bring about roughly two decades from now.
Nigeria, Indonesia, Sudan India and Brazil are projected to be among the countries most affected by the increase in land temperatures. Together, they account for more than 97,000 of the projected additional heat deaths. The United States is also among the 20 countries with the largest estimated increases, with about 3,500 additional heat deaths projected.
The estimates are based on peer reviewed methods linking temperature and mortality across more than 24,000 regions worldwide, combined with seasonal temperature forecasts. Researchers compared the projected mortality with deaths expected during the same months in an average year between 1996 and 2025.
Scientists caution that the heat impacts would come alongside other risks associated with El Niño, including drought, wildfires and changes in rainfall that could contribute to flooding. Higher temperatures could also increase pressure on agriculture, water supplies and energy systems.
Humanitarian organisations are already preparing for the changing conditions. The International Federation of Red Cross and Red Crescent Societies said its local networks were strengthening early warning systems, supporting vulnerable communities and promoting climate resilient agricultural practices.
Researchers say targeted heat response measures could reduce the immediate risks. These include heat warnings, outreach to vulnerable populations, cooling centres, hydration stations, stronger protections for outdoor workers and additional capacity in health systems.
The Climate Impact Lab researchers said the projections can help governments and humanitarian organisations identify areas where emergency resources may be needed most during the coming months.
The researchers also stressed that emergency measures alone cannot address the longer term challenge. If temperatures that are currently considered extreme become increasingly common, countries will need sustained adaptation rather than relying on repeated emergency responses.
Forecasts cited in the report suggest El Niño conditions could continue beyond February 2027 into the spring, potentially extending the period of elevated heat risk. The researchers said the projections should therefore be treated as a warning about the immediate health consequences of extreme heat as well as the longer term challenges of a warming climate.