Every revision of “Where things stand”

India is getting hotter in ways the midday thermometer does not show. Across the country the nights have warmed and humid heat has grown more common, and heat of this kind kills mostly by straining the heart, the kidneys and the lungs. Those deaths are usually written down as something else. India’s official counts of heat deaths run from a few dozen to under two thousand a year, while studies that count every death above normal put the toll of a single very hot day in the thousands. The burden falls on people who cannot stop work or get somewhere cool: farm labourers, brick moulders, delivery riders, and families in rooms under tin roofs.

The weather office counts 2024 as the warmest year since national records began in 1901, 0.65°C above the 1991–2020 average, and ten of the fifteen warmest years have come since 2011. A national average hides how the heat has changed. Measured over the whole country in a reanalysis of past weather, days that reach 40°C are about as common as they were in the 1950s, while nights that stay at or above 26°C and days of dangerous humid heat have multiplied, as the charts with that strand show. In northern India, irrigation and haze have kept winter days cooler than they would otherwise be, and researchers at Harvard warn that the historical record understates the warming to come as groundwater runs down and the air is cleaned.

Cities have warmed fastest after dark. Satellite readings of 141 cities show their ground warming at night about twice as fast as India as a whole, part of it the urban heat island, the heat that concrete and asphalt store by day and release at night. Humidity has risen too, and it matters because the body cools by sweating, which damp air slows. On a day when Mumbai’s thermometer read 33.9°C, the air felt like 46°C. The heat index captures that combination of temperature and humidity, as does the wet-bulb temperature physiologists use. India still declares a heatwave by daytime temperature, and night temperatures are not a primary criterion.

How dangerous heat is in a place depends on more than its temperature: on humidity, on how many people live there, and on how old, poor or ill they are. An index built by the Council on Energy, Environment and Water puts 57 per cent of India’s districts, home to 76 per cent of its people, at high or very high risk. The same council’s earlier index of climate vulnerability, built around floods, droughts and cyclones, left heat out, and researchers have argued that the government’s own index understates heat’s threat in the same way. Among the largest cities, Chennai, Mumbai, Kolkata and Ahmedabad rank as the riskiest for health.

Heat stroke, when the body’s temperature runs out of control, is only the visible edge of heat’s toll. Most people who die in a heatwave die of heart attacks and strokes brought on by the strain of keeping cool, and deaths begin at temperatures well below the limits of survival. Even the famous limit, a wet-bulb temperature of 35°C, is set too high: young, healthy volunteers in a laboratory could not hold their body temperature steady above about 31°C in humid air.

So the way to see what heat does is to count all deaths and compare them with what is normal for the place and season, which researchers call excess deaths. When this was done for Ahmedabad’s heatwave of May 2010, the city had 1,344 more deaths than in the same weeks of the years either side, a rise of 43%. A study of ten cities over 2008 to 2019 put heatwave deaths at about 1,116 a year in those cities alone, and researchers at Berkeley who carried its estimates to every district found that one day of extreme heat brings about 3,400 extra deaths across India. These are estimates from models with wide margins, and they measure something different from the official counts.

The evidence has a complication. The first study of temperature and death to use deaths sampled from across India, covering 2001 to 2013, found that moderately cold weather was linked to far more deaths than extreme heat. Its data end in 2013, before the heatwaves of 2015 and 2024, and its hottest band stops at a daily mean of 39.7°C, so it is no reason to think heat a minor killer. It does show how thin the national evidence still is. Some harms are barely measured at all. Women in Tamil Nadu doing heavy work in the heat miscarried at more than twice the rate of women in jobs with rest, water and shade, 5% against 2%. A review of research on how heat harms mental health found only four studies worldwide that explain it.

India keeps at least four official counts of heat deaths, and they disagree. The crime records bureau counts deaths the police record as heat or sunstroke; the disaster authority counts deaths during declared heatwaves; the weather office counts by its own heatwave days; the health ministry tracks heat stroke that hospitals report. For 2024, police records came to 1,832 deaths, the health ministry confirmed 161, and a count of news reports found 733. For 2025, when May was cooler than normal, the weather office put heatwave deaths at approximately 35. Over 2009 to 2022 the government’s own series differ by thousands of deaths.

The counts are small because a heat death is hard to certify. Under the national guidelines, a body temperature above 40.6°C at collapse marks heat stroke, but in rural areas the temperature may have fallen by the time the person reaches a big hospital, and many doctors consider it safer not to certify heat at all; some write heart attack instead. On one night in May 2024, at 47°C, seventeen government employees on election duty in Mirzapur and Sonbhadra died, and not one death had been confirmed as heat stroke weeks later. Underneath lies the death register itself: India now registers 97.2% of deaths but certifies the medical cause of only 22.0%, and in Bihar, Assam and Uttar Pradesh fewer than 6%, as the map with that strand shows. Where compensation hangs on certification, the count decides who is paid. Telangana’s revenue department recorded 38 deaths from heatwave conditions between 2019 and 2024, while police records showed 560 from heat or sunstroke.

Much of India’s work is done outdoors or in sheds without cooling: in 2023-24, 46.1% of workers were in farming and 12.0% in construction, and most work informally, without a contract, paid leave or the right to stop. The International Labour Organization found India the country most affected by heat stress at work in Asia and the Pacific, projecting the loss of 5.8% of working hours in 2030, the equivalent of 34 million full-time jobs. The Lancet Countdown estimates that heat cost 247 billion hours of work in 2024, two-thirds of them on farms, and the World Bank puts the cost across South Asia at the equivalent of 31 million full-time jobs a year, with informal workers’ earnings falling about 40% during a heatwave. Moving work to the cool of the morning helps, but less with every degree of warming; at brick kilns in Uttar Pradesh, some families now mould bricks through the night, and many workers sleep three or four hours.

Working indoors is no refuge. A survey of informal workers in Agra, Ajmer and Delhi found those in garment and stone workshops no better protected than those in the sun; outdoor workers lost about 24 working days a year to heat, and nearly one in five showed signs of kidney injury. Delivery riders in Delhi wait for orders in the sun outside the stores that send them. For women, heat cuts paid work but not the unpaid work at home. Beyond a general duty on employers, the only numerical limit on heat at work that the ILO lists for India applies to factory workrooms, under a law of 1948.

Relief from heat has to be bought. Only about 8 percent of households have air conditioning by one recent estimate, and 4.9% did in the national survey of 2020–21. Air coolers, which cool by evaporation and so work only in dry air, were in nearly half the homes of Punjab and Haryana and almost none in Kerala, Tamil Nadu and West Bengal, where the heat is humid. Projections see air-conditioner ownership rising steeply by 2040 while staying low among the poorest tenth. As cooling spreads, its share of India’s peak electricity demand is projected to rise from a tenth to nearly half by 2050, and much of that demand lasts past sunset, when solar power has faded. In May 2026 demand crossed 270 gigawatts for the first time, and coal supplied more than three-quarters of the power at peak hours. Those with least go home to rooms that hold the day’s heat into the night, and some are pushed further still. A Hijra woman whose earnings from blessing drivers at a traffic signal fell with the heat now works at night, out of the sun but in work that is unpredictable and often violent, and Dalit and Adivasi workers say heat plans do not reach them.

India’s main answer has been the heat action plan, a city’s or state’s script for what each department does in a heatwave, beginning with Ahmedabad’s in 2013 after the deaths of 2010. An early study suggests it helps: after the plan, Ahmedabad’s deaths on the hottest days rose far less, by one estimate about 1,190 deaths a year avoided, though one city over two years cannot prove the plan was the cause. But a review of 37 plans found most following a common template, only two assessing who is vulnerable and only 11 saying where the money would come from. Officials in nine cities reported water and changed working hours but little of the slower work of shade and green cover, and none had cooling for the most exposed workers. In Delhi, unions say several of the plan’s measures, such as midday breaks for builders, are not carried out.

In Ahmedabad, a housing trust is coating poor women’s tin roofs with reflective paint, and some women hold small policies that pay when the temperature crosses a set mark. That kind of parametric insurance works more like hazard pay than protection, because a worker cannot know in advance whether a day will qualify, and the Self Employed Women’s Association’s 2024 payout replaced only 5–9% of the income lost. In August 2026 the government added heatwaves to the list of notified natural calamities, opening the national and state disaster funds to relief for heat. Whether families are paid may turn on a certified heat stroke and, in some cases, a declared heatwave, which brings the question back to the count.

The record does not yet show how many Indians die of heat each year. No official series counts deaths above normal by week and district, and until one does, every figure here is either a partial count or an estimate from a model.॥