India is among the countries where babies and older people face the most heatwave exposure in the world, according to the latest Lancet Countdown on Health and Climate Change, released on October 28. The tenth edition of the report, led by researchers at University College London, also estimates that climate change caused almost 3 million heat-related deaths worldwide between 2016 and 2023.
Alongside India, the report names China, the United States and Russia as the top countries for heatwave exposure among infants and adults over 65, the two groups whose bodies cope worst with extreme heat.
What the Lancet Countdown found
The Lancet Countdown tracks dozens of indicators every year to measure how climate change is affecting human health. This year's numbers show that 2024 set the all-time record for heatwave exposure, at 15.3 billion person-days for older adults and 2.3 billion person-days for infants. Exposure eased in 2025, but it was still the second-highest year on record for the two groups combined, at 10.8 billion person-days for older adults and 1.1 billion for infants.
On average, each older adult worldwide lived through 12.8 heatwave days in 2025, and each infant 8.7 days.
The death figures are the most striking part of the report. In 2023, the hottest year in the 2016 to 2025 period, heat was linked to an estimated record 710,000 deaths, more than malaria or HIV, according to the report. About 71.5 per cent of those deaths were attributed to climate change. It is the first time the Countdown has directly estimated heat deaths caused by human-driven warming.
| Indicator | Figure |
|---|---|
| Report | Lancet Countdown on Health and Climate Change, 10th edition |
| Released | October 28, 2026 |
| Top countries for heatwave exposure (infants and elderly) | India, China, US, Russia |
| Heat-linked deaths in 2023 | About 710,000 (record) |
| Share linked to climate change (2023) | 71.5% |
| Climate-caused heat deaths, 2016-2023 | Almost 3 million |
| Heatwave days per older adult, 2025 | 12.8 |
| Heatwave days per infant, 2025 | 8.7 |
| Work hours lost to heat, 2025 | 573 billion, about $1.07 trillion in lost income |
Why India should pay attention
For India, the findings line up with what families already feel each summer. Heat stress hits hardest in homes without cooling, among outdoor workers, and among the very young and the elderly, whose bodies regulate temperature less efficiently. The report also estimates that heat exposure wiped out 573 billion potential work hours worldwide in 2025, equal to roughly $1.07 trillion in lost income, with low- and middle-income countries bearing the heaviest burden. For a country with a huge outdoor workforce in farming, construction and delivery, that is both a health issue and an economic one.
There was some good news. The report says cleaner energy and better air quality prevented around 400,000 deaths in 2023 compared with 2016, and that renewable energy growth has beaten expectations. But it calls overall climate action "grossly insufficient", noting that fossil fuels still supply about 80 per cent of the world's energy.
Practical steps to stay safe in a heatwave
- Keep infants and older family members indoors during the hottest hours, usually late morning to late afternoon.
- Make sure everyone drinks water regularly, even before feeling thirsty.
- Use light, loose cotton clothing and keep rooms ventilated or shaded.
- Watch for warning signs such as dizziness, confusion, very high body temperature or a stop in sweating, and seek medical help quickly.
- Follow local heat alerts and heat action plans issued by your city or state.
What the scientists want world leaders to do
Marina Romanello, executive director of the Lancet Countdown and a professor at UCL, said the health harms of climate change are "growing faster than the world's response to them." While real progress has been made in clean energy and health system readiness, she said, "progress has been too slow, too small, and isn't reaching those who need it most."
The authors are calling for climate change to be formally declared a global health emergency, for a new World Health Organization instrument to coordinate the global response, and for health to be placed at the centre of every climate decision. They also want climate finance for health to be given as grants rather than loans, so poorer countries can adapt without sinking deeper into debt.
What happens next
The report comes just ahead of the COP31 climate summit, where countries will negotiate new commitments on emissions and adaptation funding. Health experts in India will be watching whether the call for a health emergency gains traction there, and whether it nudges more state governments to strengthen heat action plans before next summer.
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