A strong El Niño event expected to affect the world over the next six months could be associated with more than 450,000 additional heat-related deaths, according to projections from the University of Chicago's Climate Impact Lab. Low-income countries already facing food insecurity and high energy costs are expected to face the greatest risks.
A strong El Niño event could significantly increase heat-related mortality over the coming months, according to a new research projection.
The analysis, released by the University of Chicago's Climate Impact Lab, compares projected temperature-related deaths during the current El Niño period with the level of heat-related mortality expected during a typical year.
The projection runs through February 2027.
Researchers estimate that global land temperatures could rise by approximately 1.2 degrees Celsius during the event compared with an average year, with heat-related deaths projected to be around 44 percent higher.
Developing countries face the greatest risks
The analysis suggests that countries and regions that are already hot and have relatively low incomes are likely to experience the greatest health impacts.
Developing countries and Africa's Sahel region are expected to be particularly vulnerable.
The report projects more than 66,800 additional deaths in the Sahel.
Country-level estimates highlighted in the analysis include:
- Nigeria: approximately 31,400 additional deaths
- Indonesia: approximately 19,300
- Sudan: approximately 17,600
- India: approximately 15,800
The Philippines, Vietnam, Thailand and Cambodia are collectively projected to experience approximately 19,400 additional deaths.
"A few extra degrees" can be much more dangerous
Michael Greenstone, founder of the Climate Impact Lab and an author of the study, said the greatest risks occur in places where temperatures are already high and incomes are relatively low.
"If you're already in a hot place, an extra few degrees is going to be much more dangerous," Greenstone said.
Higher-income regions generally have greater access to air conditioning, reliable water supplies and healthcare, giving them more resources to respond to extreme heat.
Heat is a growing public health threat
Extreme heat can place significant stress on the cardiovascular and respiratory systems and increase the risk of dehydration and heat-related illness.
Older adults, people with chronic diseases, outdoor workers and populations with limited access to healthcare can be particularly vulnerable.
The researchers therefore argue that El Niño should not be viewed solely as a climate or weather phenomenon, but also as a significant public health risk.
"The real measure of preparedness"
Abhiyant Tiwari, who works on heat-related issues at NRDC India, said the projections should prompt governments to strengthen their preparations for extreme heat.
Funding and implementation capacity remain important weaknesses, he said, including in countries that already have heat-action plans on paper.
Tiwari emphasized that the effectiveness of heat preparedness should not be measured simply by how many warnings are issued.
The more important question, he said, is whether those warnings actually help protect people and reduce preventable deaths.
El Niño expected to persist into 2027
The current El Niño began developing in June and is expected to rank among the strongest events on record.
El Niño is a naturally occurring climate pattern associated with unusually warm sea-surface temperatures in the tropical Pacific Ocean. Researchers have warned that climate change can amplify the intensity of temperature extremes associated with El Niño.
Earlier in September, the United Nations weather agency said there was a 100 percent probability that El Niño would continue through February 2027.
Researchers, however, caution that the health impacts and elevated heat risks associated with the event could persist into mid-2027.
The projections highlight the growing intersection between climate events and public health, particularly in lower-income countries where extreme heat can interact with food insecurity, energy costs, limited healthcare capacity and inadequate access to cooling and clean water.
