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Heat stress in India

Prelims and Mains

LeadHeat stress in India, and the cooling paradoxJune 2026

Why in news

Studies published in June 2026 found that humid heat is spreading in India beyond the summer into the monsoon, and that India has more cities among the world's most heat vulnerable than any other country. India's peak power demand reached a record in May, much of it for cooling.

Background

Heat stress is the net heat load on the body. It depends on temperature, humidity, wind and radiation, and not on temperature alone.

The body cools itself by sweating. When the air is humid, sweat does not evaporate and the cooling fails.
A heatwave is declared by the India Meteorological Department on temperature. Humid heat can be dangerous at temperatures well below that threshold.
Heat risk has three parts: exposure to the hazard, the vulnerability of the people exposed, and their capacity to cope.

What the studies found

Uncompensable heat stress, in which the body cannot cool itself at all, now affects about 8 per cent of India in summer.

At 2°C of global warming it could affect more than half the country, in the monsoon as well as the summer.
The northwest and the Gangetic plain will see humid heat in the monsoon months.
Fourteen Indian cities are among the world's fifty most heat vulnerable; Ahmedabad is second.
Across the world the warmest nights are warming faster than the warmest days, which denies the body its recovery.

Who is most exposed

Outdoor workers, and people in slum housing without ventilation, power or water.
Children: a United Nations Children's Fund report gives India the highest score for children's exposure to extreme heat.

The cooling paradox

Cooling protects people from heat, but air conditioners draw fossil power and use hydrofluorocarbons (HFCs), gases with a high global warming potential.

So cooling a room warms the planet, and the city outside the room.
Under the Kigali Amendment to the Montreal Protocol, India freezes its HFC consumption in 2028 and cuts it in phases until 2047.
The India Cooling Action Plan of 2019 aims to cut cooling demand and refrigerant demand over two decades.

The way forward

Put passive cooling first: cool roofs, shade, ventilation and building design.
Make efficient appliances and low warming refrigerants the default.
Extend Heat Action Plans to cover humid heat and warm nights, and not only daytime temperature.
Protect outdoor workers through changed working hours, water and shade.

Prelims facts

The Kigali Amendment is to the Montreal Protocol, and deals with HFCs.
HFCs do not deplete ozone but have high global warming potential.
India freezes HFC consumption in 2028.
The India Cooling Action Plan dates from 2019.

Open the lead on its own page

Heat risk is not temperature alone: it depends on humidity, radiant heat and wind, and on who is exposed and how they can cope. Summer heat stress concentrates in the Indo Gangetic plain and the coasts, driven by high temperatures and pre monsoon moisture from the Bay of Bengal. Monsoon heat stress is humid, arriving at moderate temperatures of 35 to 38°C when humidity is high, especially during monsoon breaks. An Oxford study of 205 cities over a million people placed 14 Indian cities in the global top 50 for heat vulnerability, more than any country, Ahmedabad second and Nagpur fourth, scoring hazard, vulnerability and coping capacity.

Mains: Passive cooling and low energy fans should be the first line of heat adaptation, since dependence on air conditioning raises power demand, refrigerant leaks and waste heat that warm the city further.

1970s versus now

	1970s	Now
People with at least 90 days of strong heat stress	55 per cent	70 per cent
People with at least one day of extreme heat stress	16 per cent	22 per cent

Both the long seasons of strong heat stress and the single days of extreme heat stress now reach a larger share of the world's people.Source: The Hindu, 23 June 2026

What changed

23 Jun 2026LeadHeat stress in India, and the cooling paradox

cloudburst: Sudden very heavy rain, taken by the India Meteorological Department as more than 100 mm in an hour over a small area.

State Disaster Response Fund: The fund a State draws on for relief and reconstruction immediately after a notified disaster.

State Disaster Mitigation Fund: The fund for long term works that reduce disaster risk before a disaster, rather than relief after one.

Doppler shift: The shift in a wave's frequency when its source and observer move towards or away from each other; the radar reads it to find the wind inside a cloud.

weather modification: Deliberate intervention in the atmosphere, such as seeding clouds, to change how much rain falls.

Niño 3.4 region: The equatorial Pacific box whose sea surface temperature anomaly sets the ENSO phase.

Long period average: The average June to September rainfall over 1971 to 2020, 87 cm.

Southern Oscillation: The see saw of air pressure between the eastern and western Pacific.

Uncompensable heat stress: A condition in which the body cannot cool itself by sweating because of extreme heat and humidity.

Regional Meteorological Centre: The IMD office that coordinates weather and climate services for a group of States.

Moisture adequacy index: An index of soil moisture used in assessing drought.

Trigger-1: The first alert stage of Maharashtra's Drought Management Code, based on rainfall deficiency and a dry spell of at least 21 days.

Panchnama: A field survey that records the condition of a crop.

Kallakadal: The name fishermen in Kerala give to a swell surge.

Also filed elsewhere

Forest fires · on Forests, grasslands and mountain ecosystems
Forest fires in India are tracked through alerts that the Forest Survey of India (FSI) reads off satellite passes.
Heat Action Plans · on India's climate policy: NDCs, net zero and adaptation
Extreme heat is met city by city rather than nationally, which is at once the strength of the instrument and its limit.