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Who extreme heat hits hardest

The same heatwave lands differently. Who is harmed depends on how exposed people are and what stands between them and safety.

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Five questions behind every barrier

These barriers rarely come alone. Intersections is a short note and a game about where they meet, and who protection reaches.

Smallholder and rainfed farming households

Exposed to: Work in open fields through the hottest hours, with crops and animals that depend on rain heat makes less reliable.

Held back by: Little irrigation, credit, insurance or savings, so one bad season can mean debt, sold animals and lost seed.

At the International Rice Research Institute’s farm in the Philippines, rice yields fell by about 10% for each 1 °C rise in growing-season night temperature. Peng et al., PNAS, 2004

In India, crop-damaging heat in the growing season is linked to more suicides; warming over 30 years is estimated to account for 59,300. Carleton, PNAS, 2017: crop-damaging temperatures increase suicide rates in India

What helps: Crop insurance and fair credit, Keep water in the soil, Smart irrigation and groundwater rules, Social protection floors, Mental health in heat plans

Watch: When dry soil heats the air (0:28), Hot nights and crops (0:33).

Coastal and riverine communities

Exposed to: Humid heat that stops sweat from cooling the body, warming seas that drive fish away, and warm, low water that spoils drinking supplies.

Held back by: Livelihoods tied to one place and one resource, homes on fragile land with insecure tenure, and islands and river banks far from services.

Humidity makes heat far more costly: across 2.7 million firms, ten extra days above 35 °C cut productivity by 0.75% in very humid places, more than double the average, and barely at all in dry ones. OECD Economics Department, 2024

In Viet Nam’s Mekong Delta, a long heatwave in February 2024 lowered canals and let sea water push inland; farmers who pumped the salty water onto their rice lost up to half their crop. Viet Nam News, 2024

What helps: Heat action plans, Social protection floors, Anticipatory action, Heat-ready health services

Watch: Heat, drought and salt water (0:31).

People in remote or poorly served settlements

Exposed to: Far from clinics, cool shelter, reliable power and phone signal, often at the end of the line for water and electricity.

Held back by: Warnings, ambulances and relief arrive late or not at all, and deaths here are the least likely to be counted.

What helps: Anticipatory action, Heat-ready health services, Count every heat death, Heat action plans

Watch: Clinics in a heatwave (0:33), When phones go quiet (0:34).

People in informal settlements

Exposed to: Dense rows of homes with tin, asbestos or plastic roofs, little green space, and no way to cool down at night.

Held back by: Insecure tenure means families can’t invest in cooler homes and landlords won’t, and settlements are often missing from city plans and services.

In a survey of 860 households in Ahmedabad, people in informal settlements faced temperatures up to 7.6 °C higher than people in formal housing. Mahadevia et al., 2020, reported in Frontiers in Built Environment, 2022

In Jakarta, dense low-income neighbourhoods act as heat islands; informal workers rarely have fans or air conditioning and cool off on terraces or in parks, while green space is concentrated in wealthier areas. Ufaira and others, Frontiers in Human Dynamics, 2023

What helps: Cool, affordable housing, Cool nights and support, Cooling centres and check-ins, Affordable cooling for the poorest

Watch: When home is hotter than outside (0:38), Shade follows wealth (0:36). Or see a city under strain.

Workers in heat-exposed jobs

Exposed to: Street vendors, builders, salt-pan workers, waste pickers, rickshaw and delivery workers, traffic police and sanitation staff in the hottest parts of the city; factory workers beside furnaces in unventilated sheds; then hot, crowded homes at night.

Held back by: No paid leave, contract or savings: stopping work in dangerous heat means losing the day’s income. Fixed shifts leave little room to avoid the hottest hours.

Doctors at two Indian hospitals with heatstroke units said more than 90% of the patients they treated for heat illness in 2024 were outdoor workers: security guards, migrant labourers and street vendors. Context (Thomson Reuters Foundation), 2024

In a survey of 721 Delhi street vendors in 2024, 80% saw fewer customers during heatwaves and 49% lost income. Greenpeace India and National Hawkers Federation, 2024

In Singapore, a study of 355 workers found each hot day cost a median S$21 in lost income, about 24% of a day’s median pay, and heat at workplaces was often higher than nearby weather stations showed. NUS Project HeatSafe, 2024

In Dhaka, Hanoi, Ho Chi Minh City, Phnom Penh and Karachi, garment hubs where factories trap heat, days with wet-bulb temperatures above 30.5 °C rose by 42% in 2020–24 compared with 2005–09. Cornell Global Labor Institute and Schroders, Higher Ground?

In Tamil Nadu, 68% of people face 8–9 hours a day of strong heat stress from March to June, measured by an index that counts humidity, wind and sun as well as temperature. Tamil Nadu Heat Mitigation Strategy, 2024

What helps: Heat-safe work, Income protection in heatwaves, Social protection floors, Free care for heat illness

Watch: Heat illness first aid (0:35), Work–rest cycle (0:35). Or live through a worker’s week.

Women whose livelihoods are held back by unequal access

Exposed to: Field, home-based and informal work, fetching water, and cooking in homes that trap heat.

Held back by: Less say over land, credit, technology and household decisions, and most of the unpaid care that grows in a heatwave. Without toilets at work or on transport, many drink less water. Violence at home rises with the heat.

Rural households headed by women lose about 8% more of their income to heat stress than those headed by men. FAO, The Unjust Climate, 2024

In a study of Indian women workers, 87% of those with poor or no toilets at work reported genitourinary problems, and about 1 in 10 showed heat strain and moderate dehydration. Venugopal et al., Global Health Action, 2016

In Nepal’s Madhesh Province, women cooking in hot, smoky kitchens carry a daily ‘thermal labour’ that falls hardest on women in the poorest single-room homes with little access to clean energy or credit. Ghimire and others, Frontiers in Public Health, 2025

What helps: Income protection in heatwaves, Social protection floors, Heat action plans, Cool, affordable housing, Violence prevention in heat planning

Watch: Kitchen heat (0:39).

Pregnant women, babies and young children

Exposed to: Pregnancy strains the body’s cooling, and babies overheat and dehydrate faster than adults.

Held back by: Many women keep working and fetching water late into pregnancy, and maternity and child services are rarely ready for heat.

Each 1 °C rise raises the odds of preterm birth by about 5%, and a heatwave by about 16%. Chersich et al., BMJ, 2020

In 2014–2023, each infant in India faced an average of 7.7 heatwave days a year, 47% more than in the 1990s. Lancet Countdown, India data sheet, 2024

In Tamil Nadu, among 800 pregnant women doing moderate to heavy physical work, those with high workplace heat had about twice the risk of miscarriage. Rekha et al., BJOG, 2023: occupational heat and pregnancy outcomes in 800 women workers, Tamil Nadu

Across 26 studies, each 1 °C rise in temperature was linked to about 7% more diarrhoea, a leading cause of death in young children. Carlton et al., International Journal of Epidemiology, 2016: temperature and diarrhoeal disease, 26 studies

What helps: Heat-ready health services, Heat action plans, Free care for heat illness, Social protection floors, Heat-safe pregnancy and newborn care, Safe water and rehydration for young children

Watch: Heat in pregnancy (0:37), Babies and young children in heat (0:37). Or live through a hot night.

Older people

Exposed to: Bodies that sense and shed heat less well, often with heart, kidney or lung conditions.

Held back by: Living alone, limited mobility, and warnings and help that rely on phones, apps or someone knocking on the door.

Older people in a Kolkata informal settlement were 4.3 times more likely than older people in a nearby village to face dangerous heat, with a heat index of 45 °C or more, because their homes stayed hotter than the outdoors, especially at night. Weitz, Mukhopadhyay and Das, International Journal of Biometeorology, 2022

What helps: Cooling centres and check-ins, Heat action plans, Affordable cooling for the poorest, Count every heat death

Watch: Older people and heat (0:42), Heat check-ins (0:37), Sleep in the heat (0:36). Or live through a hot night.

People with disabilities or long-term illness

Exposed to: Some conditions and common medicines, such as diuretics, interfere with the body’s cooling. Heart, kidney and lung disease and diabetes raise the danger, and heat worsens many mental health conditions.

Held back by: Warnings in formats they can’t use, cooling centres they can’t reach, and heat plans that rarely name their needs.

Heat can worsen underlying illness, including heart disease, diabetes, asthma and mental health conditions. WHO, 2026: Heat and health, fact sheet

What helps: Heat action plans, Cooling centres and check-ins, Heat-ready health services, Free care for heat illness, Mental health in heat plans

Watch: Heat, kidneys and the heart (0:35), Heat and the mind (0:31). Or live through a hot night.

Migrants, prisoners and other excluded groups

Exposed to: Hot, crowded rented rooms, cells and the hardest outdoor jobs, often in a place where they have few connections.

Held back by: No local ID, address or language can mean no warnings, clinics, rations or relief. Many migrant workers are not registered under welfare laws, such as construction workers’ boards, so they miss health and safety benefits meant for them. Who is registered, and who is known to local officials, can decide who is reached first.

Tamil Nadu’s heat strategy names prisoners, held in concrete buildings with little green space, among the groups heat plans are meant to reach, and proposes cool roofs and trees for its jails. Tamil Nadu Heat Mitigation Strategy, 2024

What helps: Cool, affordable housing, Social protection floors, Free care for heat illness, Heat-safe work

Watch: Heat in closed places (0:34).

Weather, work and the person

The same reading on a thermometer can be safe for one person and dangerous for another. How much heat the body has to carry depends on three things together: the weather, the work, and the person. Change any one and the danger changes.

The weather

Air temperature is only the start. Humidity stops sweat from cooling the body, sun and hot surfaces add radiant heat, still air removes less of it, and a hot night leaves no time to recover. Conditions at a workplace or under a roof can be worse than the nearest weather station shows.

The work

Heavy work makes heat inside the body. Protective clothing, gowns and masks hold it in. Long shifts, fixed hours and no shade or water break let it build. The same weather is a different risk for a desk worker, a builder and a nurse in protective gear.

The person

Older bodies sweat less and feel thirst later. Heart, kidney and lung disease, diabetes and pregnancy add strain, and some medicines reduce the body’s ability to lose heat. A body that did not cool down overnight starts the next day already behind.

Effects depend on exposure, task and the person. That is why a single heat alert cannot protect everyone in the same way, and why plans can ask who is doing what, in what, and after what kind of night.

Three groups heat plans often miss

People on long-term medicines. Some medicines used for long-term conditions, including some for blood pressure, heart disease, Parkinson’s and Alzheimer’s disease, blood thinners and some cancer drugs, can reduce sweating or the blood flow to the skin that carries heat away. Ageing and illness can add to the effect. Never stop or change a medicine because of the heat. Ask a doctor, nurse or pharmacist what to watch for, and plan water, shade and check-in calls for people on these medicines. Wee and Lee, Pharmacological Reviews (summary by NUS Medicine, 2023)

Health workers in protective gear. Clinics and wards fill up in a heatwave, and staff in gowns, gloves and masks carry heat they cannot shed. A survey of 3,082 health workers across six Asian places linked poor practices with protective equipment to heat-related symptoms. Its symptom scale proved unreliable, so the authors still advise staff to check their own symptoms early. Plan cool rest rooms, water, shorter rotations in full protective gear, and cooling for the clinic itself, so the people treating heat illness are not its next patients. Yang et al., BMC Nursing, 2024

Workers in hot factories and sheds. Heat is not only an outdoor problem. In a survey of 753 women at three garment factories in Phnom Penh, the share reporting heat symptoms rose from 68% in the cooler months to 88% in the hot months, as the factory heat index rose from about 25 °C to 29 °C. More said heat slowed their work and cut their motivation. These are workers’ own reports, not measured output. Plans can count indoor workplaces: measure heat where people work, cool the roof and walls, add air flow, water and breaks. Chea et al., BMC Public Health, 2025

For heat plans: Ask three questions for every group in a heat plan: how hot is it where they are, what are they doing and wearing, and what do they bring to it, such as age, illness, medicines and a night without sleep. Print the one-pager · Watch the film (1:30)

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Who extreme heat hits hardest

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The same heatwave lands differently.

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