Do Heatwaves Really Affect Women More Than Men?

Every heatwave brings the question back around, usually framed as settled fact: women are more affected by heat than men. Like many claims about sex differences in health, it turns out to be partly true, partly false, and far more interesting than the headline suggests. The population data and the physiology point in genuinely different directions, and untangling them is the key to understanding what's really going on.

TL;DR

• At the population level, women do appear slightly more vulnerable to dying in heatwaves. A 2025 meta-analysis found marginally higher heat-related cardiovascular mortality in women, and large European studies have consistently found higher heatwave mortality among women, particularly elderly women.
• But the popular explanation — that female bodies simply cope worse with heat — is largely a myth. Modern research has overturned the old belief that women thermoregulate less efficiently.
• Women maintain their core body temperature in heat just as well as men. They sweat less, but their sweat evaporates more efficiently, so the cooling result is comparable.
• Much of the mortality gap is explained by confounders, not core physiology: women live longer, so the heat-vulnerable elderly population skews female; older women have higher rates of multiple chronic conditions; and social factors play a role.
• There are some real, modest physiological differences. The menstrual cycle and hormonal contraception raise baseline core temperature slightly (around 0.2°C in the luteal phase), and some evidence suggests women store heat faster early in exercise when dehydrated.
• The practical takeaway: heat is a serious risk for everyone, the sexes are far more alike than the myth implies, and the standard precautions — hydration, cooling, pacing — apply equally to both.

What the Mortality Data Says

Start with the population-level evidence, because this is where the claim has genuine support.

When researchers examine who dies during heatwaves, women do show up as marginally more vulnerable. A 2025 systematic review and meta-analysis of heat and cardiovascular outcomes found a small but real signal: heat-related cardiovascular mortality was slightly higher in women than men. Large European studies point the same way. The EuroHEAT project, which examined heatwave mortality across European cities, consistently found higher mortality impacts among women, and several studies have specifically flagged elderly women as a particularly susceptible group. Analysis from Italy found that older women become at increased risk of heat-related death at lower temperatures than their male counterparts.

So at the level of "who actually dies in a heatwave," the answer leans, modestly, toward women. That much of the popular claim holds up. The question is why — and this is where the simple story falls apart.

The Myth of "Less Efficient" Cooling

For a long time, the assumed explanation was straightforward: women's bodies are simply worse at handling heat. This belief has been substantially overturned by modern physiology, and understanding why is genuinely illuminating.

The old view came from a real observation — that women's core body temperature tended to run higher than men's for a given heat load, and that women sweat less. From this, earlier researchers concluded women had "less efficient" thermoregulation. But later work showed this reasoning was flawed, because it didn't account for differences in body size, body composition, and fitness. When those factors are controlled for, a different picture emerges.

Women do sweat less than men. But sweating more is not the same as cooling better — much of men's heavier sweat simply drips off without evaporating, which wastes it, since it's the evaporation that actually cools. Women's sweating is more economical: they produce less, but a greater proportion of it evaporates, so they achieve comparable cooling with less fluid loss. The upshot, confirmed across multiple studies, is that women maintain their core body temperature during heat stress at essentially the same level as men. One review put it plainly: there is no good evidence that women are at greater risk of heat illness when the usual precautions around intensity, clothing, and hydration are in place. In fact, one study at a world athletics championship found female athletes used more heat-illness-prevention strategies than men.

In other words, the core machinery of human temperature regulation works about as well in women as in men. The "women cope worse with heat" story, taken as a claim about basic physiology, is largely a myth.

So Why Do More Women Die?

If the physiology is broadly equal, the mortality gap needs another explanation — and the evidence points overwhelmingly to confounding factors rather than any inbuilt female frailty in the heat.

The biggest is age. Women live longer than men on average, which means the very elderly population — by far the most vulnerable group in any heatwave — contains more women than men, simply because more women survive to those ages. When a heatwave's deaths concentrate among the over-80s, and the over-80s are disproportionately female, the death toll skews female without female physiology being the cause. It's a demographic effect, not a thermoregulatory one.

Layered on top is health. Older women have higher rates of multi-morbidity — living with several chronic conditions at once — than older men. Many of those conditions, and the medications used to treat them, impair the body's ability to handle heat: some affect sweating, some affect fluid balance, some affect the cardiovascular adjustments heat demands. A body already managing several illnesses has less reserve to cope with the added strain of extreme heat. Social factors compound it further, including that elderly women are more likely to live alone, which raises the risk during a heat emergency.

So the mortality signal is real, but its roots lie mostly in longevity, age, illness, and circumstance — not in any fundamental inability of the female body to regulate heat. It is a story about who the vulnerable elderly are, more than about sex differences in cooling.

The Real Physiological Differences

None of this means the sexes are identical in the heat. There are genuine physiological differences — they're just more specific, and more modest, than the blanket claim implies.

The clearest involves sex hormones and the menstrual cycle. A woman's baseline core body temperature varies across the cycle, running around 0.2°C higher during the luteal phase (the roughly two weeks after ovulation) than the follicular phase. Hormonal contraception can produce a similar sustained rise. This shift is small, but it means a woman in the luteal phase starts from a slightly higher core temperature and reaches the point of active cooling at a marginally higher threshold — a real, if minor, modifier of the heat response. The hormonal fluctuations of the cycle genuinely do affect thermoregulation, which is one authentic sex difference the research supports.

There's also some evidence around dehydration. One study found that when dehydrated, women showed a faster rise in core temperature at the very start of exercise in the heat than men did — suggesting greater early heat storage under mild dehydration, an effect not changed by cycle phase. This is a narrower finding and shouldn't be overstated, but it points to hydration mattering as much for women as for men, perhaps more so at the outset of exertion.

These are the real differences: cyclical, hormonal, generally small. They're a world away from the sweeping notion that women's bodies simply can't handle heat as well.

What This Means in Practice

For everyday purposes, the practical implications are reassuringly simple, and they apply to everyone.

Heat is a serious health risk for both sexes, and the core protective measures don't differ: stay hydrated, keep cool, avoid the hottest part of the day, dress lightly, and check on the vulnerable. The practical basics of staying cool in a heatwave apply equally to both sexes, and for anyone with high blood pressure, the extra care needed in hot weather matters more than sex does. The people who genuinely warrant extra attention in a heatwave are defined less by sex than by age, health, medication, and isolation — the elderly, those with chronic conditions, those on certain drugs, and those living alone. That group happens to contain more women, which is why targeted heat-health advice often reaches more women, but the vulnerability tracks age and illness, not femaleness as such.

For younger, healthy women, the takeaways are minor and specific rather than alarming: be aware that heat tolerance may feel slightly different across the menstrual cycle, and take hydration seriously, particularly before exercising in the heat. Beyond that, the same rules serve everyone. The myth to discard is the idea that being female is itself a meaningful heat-risk factor. The reality is that human bodies, male and female, are strikingly similar in how they cope — and that the differences in who suffers most come mostly from age and health, not from sex.

Frequently Asked Questions

Do heatwaves affect women more than men?

At the population level, women die slightly more often in heatwaves — a 2025 meta-analysis found marginally higher heat-related cardiovascular mortality in women, and European studies consistently find higher heatwave mortality among elderly women. However, this is largely explained by women living longer (so the vulnerable elderly skew female) and higher rates of chronic illness in older women, rather than female bodies being worse at handling heat.

Are women's bodies worse at cooling down than men's?

No — this is a common myth. Modern research shows women maintain their core body temperature in heat just as well as men. Women sweat less, but their sweat evaporates more efficiently, so the cooling effect is comparable. The older belief that women thermoregulate "less efficiently" came from not accounting for differences in body size and fitness.

Why do more women than men die in heatwaves, then?

Mostly because of confounding factors rather than physiology. Women live longer, so the very elderly — the most heat-vulnerable group — are disproportionately female. Older women also have higher rates of multiple chronic conditions and the medications that treat them, many of which impair heat tolerance, and are more likely to live alone. The mortality gap reflects age, health, and circumstance more than sex.

Does the menstrual cycle affect how women handle heat?

Slightly. Core body temperature runs around 0.2°C higher during the luteal phase (the two weeks after ovulation) than the follicular phase, and hormonal contraception can cause a similar rise. This means a woman in the luteal phase starts from a marginally higher core temperature. It's a real but small effect, not something that makes women broadly unable to cope with heat.

Should women take different precautions in a heatwave?

Largely no — the core measures are the same for everyone: stay hydrated, keep cool, avoid peak heat, and check on the vulnerable. Women may find heat tolerance feels slightly different across the menstrual cycle, and hydration with electrolytes is worth prioritising before exercising in heat. The people needing most care in a heatwave are defined by age, health, and isolation rather than sex.

Who is most at risk in a heatwave?

The elderly, people with chronic health conditions, those taking certain medications, young children, and people living alone. This group includes more women largely because women live longer, but the risk tracks age and health rather than sex itself. Anyone in these categories, of either sex, should take extra care and be checked on during extreme heat.

The Bottom Line

So do heatwaves affect women more than men? The honest answer is: slightly, at the population level — but not for the reason most people assume. Women do show a small excess of heat-related deaths, yet this is driven largely by living longer, ageing into the most vulnerable years, and carrying more chronic illness, rather than by any fundamental female disadvantage in regulating heat.

On the physiology itself, the sexes are far more alike than the myth suggests. Women maintain their core temperature in heat as effectively as men, cool themselves through more efficient sweating, and face no greater risk of heat illness when sensible precautions are in place. The genuine differences — the modest hormonal shifts across the menstrual cycle, the hydration nuance — are real but minor.

The useful message is the one that serves everyone: heat is dangerous, the precautions are the same, and the people who most need protecting are defined by age and health, not by sex. Discarding the myth doesn't make heat less serious — it just points our attention at the things that actually matter.

Related Reading

• How to Stay Cool in a Heatwave
• Managing High Blood Pressure in the Heat
• Tropical Nights: Why You Can't Sleep in a Heatwave, and What Helps

Popular Articles