El Niño is approaching record intensity, with sea-surface temperatures in the tropical Pacific already reaching levels comparable with those recorded at the peak of the record-setting event in 2015. A study by Climate Impact Lab, a research centre at the University of Chicago, estimates that extreme heat associated with the current phenomenon could cause 451,000 additional deaths between September 2026 and February 2027.
The World Meteorological Organisation expects El Niño to reach its maximum intensity towards the end of this year. By mid-September, the temperature anomaly in the tropical Pacific area at the centre of the phenomenon had exceeded 3 degrees Celsius, reaching a level similar to that recorded in November 2015, when El Niño reached its previous peak.
El Niño is a recurring natural phenomenon involving unusually warm surface waters in the tropical eastern Pacific. Its effects can extend across the world, influencing temperatures and rainfall patterns. Researchers say the current event is particularly significant because it is occurring while global temperatures are already elevated by climate change.
The Climate Impact Lab researchers calculated heat-related deaths for the six months from September 2026 to February 2027, although they acknowledge that the final number could be higher because the effects of El Niño are expected to continue beyond that period. The projected 451,000 deaths, they said, illustrate the scale of the potential impact.
The overwhelming share of the projected deaths is expected to occur in the Global South. The study estimates that countries in the Sahel could record 66,800 additional heat-related deaths during the six-month period compared with a normal year. Nigeria alone is projected to account for 31,400 of those deaths, followed by Sudan with 17,500, Niger with 10,000 and Chad with 8,000.
In south-east Asia, the study projects 19,400 additional heat-related deaths in the Philippines, Vietnam, Thailand and Cambodia combined, and 19,300 in Indonesia. India is projected to record 15,800 additional deaths, while Brazil is expected to record 13,300.
Emily Grover-Kopec, one of the study’s authors, attributed the unequal distribution partly to seasonal differences. The six-month forecast covers summer in the southern hemisphere, when temperatures reach their annual maximum, while it covers winter in the northern hemisphere, when temperatures are generally at their lowest. She also pointed to differences in resilience and access to measures that can reduce heat-related mortality, saying poorer regions tend to experience more deaths than wealthier regions exposed to similar temperatures.
In Spain, the study projects 477 heat-related deaths linked to the event, including 362 in September. Madrid is expected to record 130 deaths, the highest figure among Spain’s regions and the second-highest among European regions after Lombardy in Italy. Grover-Kopec warned that heat-related deaths in the northern hemisphere are expected to increase as spring and summer approach.
The researchers said heat-related deaths represented only part of the expected consequences. Higher temperatures and changing rainfall patterns could also contribute to droughts, wildfires and floods, while the current El Niño “could become the strongest ever recorded”.
The effects are already being reported in several regions. Reduced rainfall associated with El Niño is worsening fires that have burned for weeks on Indonesia’s Sumatra and Borneo islands, where fires linked to the palm oil industry have contributed to deforestation. In California, Governor Gavin Newsom declared a state of emergency on Monday to strengthen preparations for El Niño, while the Caribbean coast of Colombia has also experienced several days of extreme heat.
Measurements of El Niño and its opposite, La Niña, use the central equatorial Pacific’s Niño 3.4 region as a reference. Data collected by Climate Brink showed a temperature anomaly of 3.07 degrees Celsius there on 19 September, using 2005-2025 as the reference period. Researchers Andrew Dessler and Zeke Hausfather expect the anomaly to reach 4 degrees Celsius in November, when the current El Niño is forecast to reach its peak.
