How Many People Die in Heatwaves? The Silent Summer Death Toll

Picture a top-floor flat in a European city in the middle of a July heatwave. The windows face south and do not open wide. Inside, an 84-year-old woman lives alone. She does not feel especially thirsty, because the sense of thirst fades with age. She does not want to bother anyone. The thermometer on the kitchen wall reads 33 degrees at ten at night.

Nobody will see her collapse. She will not be on the news. When the statisticians finally count the summer's excess deaths, months later, she will be one of tens of thousands, most of them old, most of them alone, almost none of them recorded as having died of "heat".

That is the strange thing about heatwaves. They are among the deadliest natural hazards on earth, and almost nobody sees them kill.

The headline number

The most widely cited global estimate comes from a large study published in The Lancet Planetary Health in 2021, which analysed daily deaths and temperatures across 43 countries and extrapolated to the world. It found that around 489,000 deaths a year were associated with heat between 2000 and 2019. That is roughly 1,340 a day on average, although in reality heat deaths are concentrated into the hottest weeks of the year.

Time period	Heat-related deaths (average, approx.)
Per year	489,000
Per month	41,000
Per week	9,400
Per day	1,340
Per hour	56
Per minute	0.9

To put that in context, heat kills more people each year than malaria, and close to as many as HIV/AIDS. You can see how those causes compare in real time on our live death counter.

The same study found that cold is still deadlier overall, killing around ten times as many people. We explain why in why winter kills more people than summer. But cold deaths are slowly falling while heat deaths are rising, and heat waves arrive in sudden, deadly bursts in a way that cold rarely does.

Europe: the continent where heat kills most

Per person, Europe has the highest heat mortality of any region. It has an old population, many cities designed for a cooler climate, and few homes with air conditioning. A series of studies led by researchers at ISGlobal in Barcelona has estimated heat deaths for recent European summers.

European summer	Estimated heat-related deaths
2003	Around 70,000
2010 (Russia and Eastern Europe)	Around 55,000 in Russia alone
2022	Around 61,700
2023	Around 47,700
2024	Around 62,700

The summer of 2003 was the event that changed how Europe thinks about heat. Around 15,000 people died in France in a little over two weeks in August, many of them elderly people alone in Paris apartments while families were away on holiday. Hospitals and morgues were overwhelmed. Afterwards France introduced a national heat plan, with registers of vulnerable people and checks on them during heatwaves.

Southern Europe bears the heaviest load relative to population. Italy, Spain, Greece and Portugal consistently have the highest heat death rates per million people. You can see how overall mortality in each compares on our Europe region page, or look at individual countries such as Italy, Spain and Greece.

The UK picture

Britain is not usually thought of as a hot country, but heat deaths there are real and rising. During the summer of 2022, when temperatures in England passed 40 degrees for the first time on record, the UK Health Security Agency estimated close to 3,000 excess deaths in England during that summer's heat episodes, mostly among people aged 65 and over.

UK heat fact	Detail
Record temperature	40.3 degrees at Coningsby, Lincolnshire, July 2022
Excess heat-period deaths in England, 2022	Close to 3,000
Most vulnerable	People over 75, especially living alone
Typical setting	Homes, not hospitals
Biggest risk factor indoors	Overheating flats and top-floor rooms

For context on everyday mortality, see how many people die in the UK every day.

Who heat kills

Heat does not kill evenly. It finds the people whose bodies cannot cool down, and the people who cannot get away from it.

Group	Why they are at risk
People over 75	Weaker thirst, less sweating, heart and kidney strain
People living alone	Nobody notices the warning signs
People with heart or lung disease	Heat forces the heart to pump harder
People with kidney disease or diabetes	Dehydration and electrolyte problems
People on certain medicines	Diuretics and some psychiatric drugs affect temperature control
Outdoor workers	Hours of exertion in direct sun
Babies and young children	Less able to regulate temperature
Homeless people	No escape from heat

The majority of heat deaths are not heatstroke in the classic sense. They are heart attacks, strokes, kidney failure and breathing problems triggered or worsened by heat. That is why so few death certificates mention heat at all, and why the true toll only shows up in excess deaths. Most victims are in the 70 to 84 and 85 and over age groups. Heat also adds pressure on the heart, and we explain the mechanics on our cardiovascular disease page.

Heat beyond Europe

Europe has the best data, but some of the deadliest individual heatwaves have struck elsewhere.

Event	Estimated deaths
Russia, summer 2010	Around 55,000
India, May to June 2015	More than 2,000
Karachi, Pakistan, June 2015	Over 1,000
Chicago, July 1995	Around 700
Pacific Northwest, US and Canada, June 2021	Several hundred, including over 600 in British Columbia
Hajj pilgrimage, Saudi Arabia, June 2024	Over 1,300 pilgrims

In much of South Asia, Africa and the Middle East, heat deaths are badly undercounted because death registration is incomplete. Researchers believe the true toll in India and Pakistan alone is far higher than recorded. The 2015 Karachi heatwave was made worse by power cuts that turned off fans and water pumps during the hottest days, a reminder that heat kills through infrastructure as much as through weather. See how mortality patterns differ across the continent on our Asia region page.

Why the toll is rising

The Lancet Countdown on health and climate change estimates that heat-related deaths among people over 65 have risen sharply since the 1990s, by well over 100%. Two forces are pushing in the same direction.

Driver	Effect
Warmer summers	More days above the temperature at which deaths start to climb
Ageing populations	More people in the age groups most vulnerable to heat
Urban heat islands	Cities can be several degrees hotter than the countryside, especially at night
Hot nights	Bodies cannot recover when temperatures stay high overnight
Energy costs	People avoid using fans or air conditioning to save money

Hot nights matter more than most people realise. A hot day followed by a cool night is survivable for most people; the body recovers. A string of nights that stay above 20 degrees does not give the heart a rest, and that is when deaths climb fastest.

Knowing the warning signs

Many heat deaths happen because nobody recognises how ill someone has become until it is too late. Heat exhaustion is common and treatable. Heatstroke is a medical emergency, and in an older person it can develop with little obvious warning.

Condition	Typical signs	What to do
Heat exhaustion	Headache, dizziness, heavy sweating, nausea, cramps, intense thirst	Move somewhere cool, lie down, drink water, cool the skin
Heatstroke	Confusion, slurred speech, hot skin that may stop sweating, fast breathing, seizures, collapse	Call emergency services at once and cool the person while waiting
Dehydration in older people	Dark urine, drowsiness, confusion, falls	Offer fluids regularly, check medicines with a doctor

The NHS advice is that someone with heat exhaustion should start to feel better within about 30 minutes of cooling down and drinking water. If they do not, or if they become confused, it should be treated as heatstroke.

Confusion is the sign to watch for most closely in older relatives. A person who seems muddled, drowsy or not themselves on a very hot day may be far more unwell than they look, and they are often the last to say so. Falls are another hidden marker: dizziness and low blood pressure in the heat lead to falls in older people, which carry their own risk, as we cover in how many people die from falls every day.

What actually saves lives

Heat deaths are some of the most preventable in this whole field. Most of the protection is simple.

Measure	Why it works
Heat-health warning systems	Give hospitals, care homes and families time to prepare
Checking on older neighbours and relatives	The single most effective personal action
Drinking water regularly, before feeling thirsty	Older people's thirst signal is weak
Cool rooms and cooling centres	A few hours somewhere cool each day lowers risk
Closing curtains on sunny windows	Keeps indoor temperatures down
Fans with care	Useful in moderate heat; less helpful above body temperature
Changing work hours	Moving outdoor work to early morning
Greener cities	Trees and parks lower local temperatures

After the 2003 disaster, France built a heat plan. When a similar heatwave struck in 2006, researchers estimated that several thousand fewer deaths occurred than the 2003 pattern would have predicted. Planning works.

Heat, work and the future

Heat is increasingly a workplace issue too. The International Labour Organization estimates that excessive heat causes nearly 19,000 work-related deaths a year, mostly among outdoor workers. We cover that in how many people die at work every day.

For the wider picture of weather, floods, storms and earthquakes, see how many people die in natural disasters every year. Heatwaves are often left out of disaster rankings because their victims are hard to count, but in many years they are the deadliest natural hazard of all.

While you were reading this

You have spent about 12 minutes with this article. On an average day across the year, around 11 people die from heat-related causes in that time. During a major European heatwave, that number in Europe alone can be several times higher.

Across all causes, roughly 1,400 people have died worldwide in the same 12 minutes. You can watch that number rise on our live death counter and follow today's totals on our deaths today page.

The next time a heatwave is forecast, the most useful thing most of us can do takes five minutes: call or knock on the door of someone older who lives alone.

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Data sources: Zhao et al. (2021), The Lancet Planetary Health, global mortality associated with non-optimal temperatures; Ballester et al. (2023) and Gallo et al. (2024), Nature Medicine, heat-related mortality in Europe; ISGlobal estimates for summer 2024; UK Health Security Agency heat mortality monitoring; Lancet Countdown on Health and Climate Change; International Labour Organization. Figures are rounded and represent modelled estimates with wide uncertainty ranges; heat deaths are mostly counted as excess deaths rather than from death certificates. This article is for informational purposes only and does not constitute medical advice.