Nigeria could record an estimated 56,000 additional heat-related deaths during a six-month period ending in March 2027 as extreme heat associated with the ongoing El Niño event threatens populations across the country, according to a forecast by the Climate Impact Lab at the University of Chicago.

The Lab’s El Niño Heat Mortality Tracker estimates that about 857,400 additional heat-related deaths could occur globally between June 2026 and March 2027, compared with a historical baseline. Of this total, approximately 372,900 deaths are projected for October 2026 to March 2027.

The tracker identifies Nigeria as the country with the highest projected heat-related mortality over the six-month forecast period, narrowly ahead of India, where about 55,000 additional deaths are projected.

The estimates are model-based projections, not confirmed deaths. They represent the estimated increase in heat-related mortality relative to the historical baseline rather than the total number of deaths expected from all causes.

Global heat risks

The tracker estimates that about 484,500 additional heat-related deaths occurred between June and September 2026. Combined with the forecast for October to March, the projected total reaches approximately 857,400 deaths over the period.

Other countries facing substantial projected heat-related mortality include Indonesia, with about 29,000 additional deaths, and Brazil, with approximately 19,000 over the six-month forecast period.

The Climate Impact Lab said the updated estimates were significantly higher than those in its September 2026 report, partly because the latest tracker incorporated March into the forecast period and replaced earlier temperature forecasts for August and September with observed data.

According to the Lab, August 2026 was the warmest August on record, while September was the second warmest September.

How estimates were calculated

The tracker uses research on the relationship between daily temperatures and all-cause mortality, accounting for differences in local climate, vulnerability and the capacity of communities to adapt to heat.

For months that have already elapsed, the researchers use ERA5 global reanalysis temperature data. For the forward-looking forecast, they use the European Centre for Medium-Range Weather Forecasts’ SEAS5 seasonal prediction system.

The resulting estimates compare projected temperature-related mortality with the 1996–2025 average, according to the tracker’s methodology.

The Lab said the tool provides estimates for approximately 3,700 state- and provincial-level regions worldwide. It is intended to help governments, funders and other decision-makers identify areas where heat protection and emergency interventions may be most needed.

The researchers also cautioned that full details of the mortality estimation method would be published in an upcoming peer-reviewed journal.

Calls for preparedness

The tracker identifies early-warning systems, expanded healthcare access, reliable drinking water and cooling centres as interventions that can help reduce the risks associated with extreme heat.

For Nigeria, the projection raises questions about the availability of heat-health warnings, public guidance and emergency preparedness as temperatures rise.

However, the national estimate alone does not establish which Nigerian states or population groups face the greatest risk, nor does it demonstrate whether government preparedness measures are adequate. State-level data and further reporting would be needed to identify the most exposed communities and assess existing responses.

The projections also should not be interpreted as evidence that all the estimated excess deaths will be caused exclusively by El Niño. The tracker models changes in temperature-related mortality against a historical baseline.

The Climate Impact Lab plans to update the tracker monthly through the conclusion of the current El Niño event, providing new estimates to support decisions on heat-risk reduction and public-health preparedness.