A report by the Climate Impact Lab, a research group at the University of Chicago, released on Wednesday, 23 September 2026, estimates that El Niño-driven heat could cause as many as 451,000 additional heat-related deaths between June 2026 and the end of February 2027, compared with deaths expected in a typical year, according to the Associated Press.

The Sahel is expected to be the hardest-hit region, with about 66,800 additional deaths. The report also projects about 19,400 additional heat deaths combined across the Philippines, Vietnam, Thailand and Cambodia, 19,300 in Indonesia, 15,800 in India and 13,300 in Brazil, according to AP. The study combined seasonal temperature forecasts from the European Centre for Medium-Range Weather Forecasts (ECMWF) with local estimates of how heat affects mortality across more than 24,000 regions worldwide. Michael Greenstone, a co-founder of the group and co-author of the study, told AP the danger is likely to persist beyond February, when the current El Niño is expected to have ended.