Hyderabad: India loses roughly 3,400 people on every day extreme heat strikes, according to a study published in Frontiers in Environmental Health, a figure that dwarfs the approximately 800 heat-related deaths the government officially records in an entire year.
The research, conducted by Piyush Narang and Ashok Gadgil from the India Energy and Climate Centre at the University of California, Berkeley, produces the first district-level estimates of heatwave mortality across the country.
Building on study of 10 Indian cities
It builds on an earlier epidemiological analysis of 10 Indian cities and extends those findings to all 765 districts using climate zone classifications.
“As extreme heat events become more frequent and intense under climate change, failure to act on such evidence is likely to result in continued large and avoidable loss of life,” the authors write.
Why official numbers collapse
The gap between 3,400 and 800 does not reflect a counting error. It reflects how India records death.
When heat kills, it rarely does so directly. It worsens heart disease, strains kidneys, accelerates respiratory failure. A doctor writes the cause of death as cardiac arrest. Heat never appears on the certificate.
The researchers point to 2023 as an example of how this plays out. Between March and July that year, Heatwatch and the Veditum India Foundation tracked 733 heatstroke-related deaths through media reports alone. The Union Health Ministry officially reported 360 during the same period, less than half.
“Heat impacts are captured through excess all-cause mortality rather than cause-specific coding,” the paper states.
Excess mortality, the count of deaths above what a population would normally experience, captures what official figures miss. It asks not how people died, but how many more died than expected. That method produces the 3,400 figure.
Five days, 30,000 dead
The one-day figure compounds when heat persists.
A five-day heatwave, the paper estimates, produces nearly 30,000 excess deaths nationally. The near-ninefold jump from 3,400 to 30,000 reflects two forces working together: the body accumulates heat stress across consecutive days and the risk coefficient per day rises the longer extreme heat continues.
“Strengthening mortality surveillance, improving access to high-resolution temperature data and integrating heatwave preparedness into district-level public health and disaster management systems are critical steps toward reducing preventable deaths from extreme heat in India,” the authors write.
If each district were to experience five such heatwaves across a single summer, the paper describes this as a planning scenario, not a forecast; national excess mortality would reach approximately 1,50,000 deaths per year.
Where the burden falls
The deaths do not distribute evenly.
Uttar Pradesh alone accounts for roughly 8,056 excess deaths during a five-day heatwave. Bihar follows with approximately 3,615, then Madhya Pradesh at 2,964; Rajasthan at 2,664 and Gujarat at 2,354. Together these five states, home to 43 per cent of India’s population, absorb more than 60 per cent of projected excess deaths.
At the district level, Ahmedabad leads with an estimated 307 excess deaths during a single five-day event. Jaipur follows with 265 and Surat with 261. Prayagraj, Patna, Lucknow, Kanpur Nagar, Azamgarh, Agra and Bareilly each cross 180 deaths.
Every district on that list sits in northern or western India.
The concentration carries an economic dimension the paper quantifies using Gini coefficient analysis. The five highest-burden states contribute only 29 per cent of India’s GDP while absorbing 66 per cent of projected heatwave excess deaths. The researchers describe this as a ‘2.3-fold disproportion between mortality burden and economic capacity.’
“The states least able to finance adaptation are precisely those facing the greatest heat mortality risk,” the paper states. “Failing to account for this disproportion when sizing and directing heat resilience investments will systematically under-resource the populations most at risk.”
South India’s invisible burden
Southern India presents a different problem, not high numbers, but missing ones.
The study uses dry-bulb temperature to define heatwaves, consistent with the epidemiological work it builds on. In humid coastal districts across Tamil Nadu, Kerala, Andhra Pradesh and Karnataka, along with Telangana, that threshold fails to capture days when heat and humidity combine to produce dangerous physiological stress at lower temperatures.
‘Genuine heatwave events may be missed’ in these areas, the paper acknowledges.
Parameters of measuring heat across Hyderabad
Hyderabad functions in the study not as a data point but as a climate-risk anchor.
The researchers assign much of the Deccan Plateau, including Telangana, to a ‘Hyderabad’ heat-risk cluster and apply risk coefficients derived from the city to surrounding districts. Yet no standalone excess death figure for Hyderabad district appears in the published results.
The paper calls for future studies to incorporate wet-bulb temperature metrics, which adjust for humidity and better reflect what the human body actually endures. Until that work happens, Southern India’s heat burden remains estimated low, not because the risk is absent, but because the tools used cannot fully see it.
What the researchers want
The paper argues India needs district-level heat action plans, stronger early warning systems and heat-relevant healthcare infrastructure.
It calls for public access to district-level daily mortality data, which would allow researchers to estimate local risk directly rather than extrapolate from 10 cities.
“District-level estimates, even based on these approximations and simplifications, are highly valuable for identifying high-risk areas, allocating resources appropriately and efficiently, and designing locally appropriate heat action plans,” the authors write.
India currently models its national heat response on Ahmedabad’s 2010 heat action plan. The researchers argue that a city-level framework, however effective, cannot address the structural concentration of heat mortality in states that lack the fiscal capacity to replicate it.
The 3,400 figure, they suggest, demands something larger.
