The ongoing ‘Super’ El Niño could lead to an estimated 239,000 additional deaths globally from extreme hot days between September 2026 and February 2027, according to a new report by the Climate Impact Lab of the University of Chicago, which warns that much of the mortality burden will fall on countries in the Global South.
The Sahel is forecast to see the largest increase, with 66,800 additional heat-related deaths between September and February, including 31,400 in Nigeria, while India is projected to record 15,800 additional deaths. Indonesia could see 19,300, Southeast Asia -- including the Philippines, Vietnam, Thailand and Cambodia -- 19,400, and Brazil 13,300.
The timing of the deaths was also expected to vary considerably. Between December 2026 and February 2027 alone, Nigeria and Indonesia were projected to see 15,400 and 10,400 additional heat-related deaths, respectively, while Brazil could record 8,000 and India 7,400.
This meant nearly half of India’s projected 15,800 additional deaths over the six-month period could occur in these three months.
The death toll, however, could be much higher over the course of the El Niño. While 239,000 additional heat-related deaths are projected between September 2026 and February 2027 globally, the researchers estimated that overall, 451,000 additional deaths could occur from the start of the event in June 2026 through February 2027.
They cautioned that the toll could rise further as unusually warm conditions are expected to persist into mid-2027.
The report warned that the unusually high temperatures driving these deaths offer a glimpse of a much hotter future, highlighting that the conditions expected during this El Niño resemble temperatures that climate change projections suggest could become normal and the scale of the mortality risk from these temperatures could become commonplace around 20 years from now.
Global land temperatures were projected to be about 1.2 degrees Celsius above normal in the coming months, driven in large part by the current El Niño, which began in June and is expected to persist through the Northern Hemisphere spring.
The report estimated that these conditions could result in 44 per cent more extreme hot days than in a normal year.
“We have long been able to predict the impacts of temperatures on crops, and now we can predict their impact on the worst outcome—death. The result is that we now can estimate that 451,000 people may die in the coming months due to El Niño. This is such a large number that it can be numbing, but it is made up of parents and children, grandparents and neighbors, people going to work, caring for families, and living their lives,” says Michael Greenstone, a co-founder of the Climate Impact Lab and the Milton Friedman Distinguished Service Professor in Economics at the University of Chicago.
“This report allows decision-makers to see exactly where emergency actions can be taken now to save tens of thousands of lives in the coming months.”
The estimates were based on the Climate Impact Lab’s existing research on the relationship between temperature and excess mortality, adjusted for differences in local climate, vulnerability and capacity to adapt. The researchers applied these relationships across 24,378 regions worldwide to long-range temperature forecasts from the ECMWF SEAS5 seasonal forecasting system.
They then estimated how many additional heat-related deaths would occur compared with the 1996-2025 average, while also accounting for uncertainty in both the temperature forecasts and the temperature-mortality relationship.
The timing of the projected deaths varied considerably across countries, giving governments and humanitarian agencies a window to intervene, the report said.
For India, the risk was expected to extend beyond the current six-month forecast. The researchers said heat-related deaths could continue to rise in India and Pakistan as they move towards the summer of 2027, with unusually warm conditions expected to persist beyond February.
The Climate Impact Lab said it would update its projections as the El Niño progresses.
The report argued that targeted emergency measures could still prevent tens of thousands of deaths. It identified heat warnings, health outreach to vulnerable populations, cooling centres and hydration stations, protections for outdoor workers and increased health-system capacity among measures that could reduce the impact of extreme temperatures.
But emergency measures alone would not be sufficient as temperatures that are exceptional today become increasingly common.
The researchers called for greater investment in longer-term adaptation, including better temperature forecasting, heat action plans, and wider access to cooling technologies, as well as more evidence on which interventions work across different regions, climates, and health systems.
“Increasing emergency response and better targeting our efforts can save many lives this year. But 20 years from now, once today’s extreme temperatures become the new normal, we don’t want to be in a constant state of emergency,” says report co-author Tamma Carleton, Faculty Head of Research for the Climate Impact Lab and an Assistant Professor at the University of California, Berkeley.
“We need to mobilize resources now to design, deploy, and evaluate the preparation and planning tools that will save lives in the years ahead.”