Can We Train Our Bodies to Cope Better With Hot Weather?

Britain may not traditionally be thought of as a hot country. But periods of extreme heat are becoming increasingly relevant to public health.

For some people, hot weather is unpleasant. For others, it can be dangerous. Older adults and people with certain long-term health conditions may be more vulnerable to dehydration, heat exhaustion, heatstroke, cardiovascular strain and kidney problems.

That makes the public-health message straightforward: when hot weather arrives, protect yourself, follow current NHS and UKHSA advice, and take symptoms seriously.

But is our ability to cope with heat completely fixed as we get older?

Emerging research suggests not necessarily.

Why can heat become harder to handle?

When the body becomes hot, it tries to lose heat in several ways. Blood flow to the skin increases. Sweating begins. Evaporation from the skin carries heat away.

With ageing, some of these responses can become less effective. Older adults may sweat less effectively, have reduced skin blood-flow responses or experience a greater rise in core temperature under the same heat load.

That does not mean every older person responds in the same way. Ageing is gradual and individual. Fitness, hydration, medical conditions, medicines, mobility and the environment all affect how someone tolerates heat. Some medicines can affect sweating, blood pressure, fluid balance or kidney function, so a medicine review may be more useful than guessing from age alone.

What is heat acclimation?

Repeated exposure to heat can trigger physiological adaptation. Over time, the body may begin sweating sooner, improve its sweating response, increase skin blood flow sooner, reduce resting core temperature and experience less cardiovascular strain during a similar heat exposure.

This process is called heat acclimation. It is well established in athletes, military personnel and workers in hot environments. The interesting question is whether older adults retain a similar capacity to adapt.

The hot-bath study

A 2026 study in The Journal of Physiology compared 15 adults aged 60–78 with 16 adults aged 21–40. Participants completed seven consecutive days of passive heat acclimation using hot-water immersion. The researchers measured signals including skin sympathetic nerve activity, sweating, skin blood flow, core temperature and heart-rate responses.

After acclimation, both age groups showed earlier activation of heat-loss responses and a lower resting core temperature. The changes in the older group were broadly comparable with those in the younger group.

That is a fascinating finding about the ageing body's remaining adaptability. It is not a home-treatment instruction.

Another small study found something similar

A 2026 UK study looked at nine recreationally active participants with an average age of around 76. After four days of hot-water immersion, participants showed improved exercise capacity during heat exposure.

Again, this is promising. It also involved very small numbers and healthy, active volunteers. It does not establish a public-health protocol for older adults generally, or for people with medical conditions or multiple medicines.

A 2023 systematic review reached a similarly balanced conclusion: short-term heat-acclimation protocols appear feasible in older adults, but the evidence remains limited and passive hot-water immersion needs further study.

The bigger message is more interesting

The most important finding may not be “hot baths are good”. It may be:

The older body can still adapt.

Ageing can change physiology, but change does not automatically mean complete loss of adaptability. That matters for fitness, strength, balance, heat tolerance, learning and resilience.

Ageing changes the body. It does not necessarily remove its ability to adapt.

Why heat is different from exercise

Exercise generates heat, which is one reason traditional heat-acclimation programmes often combine exercise with a hot environment. But strenuous exercise in heat may not be appropriate for many older adults.

Researchers are therefore interested in passive approaches such as hot-water immersion and sauna exposure. These may create a heat stimulus without requiring hard physical exercise. Passive heat is not automatically low risk, however. The body still has to manage a substantial rise in temperature, blood flow and fluid demand.

Who should be particularly careful?

Deliberate heat exposure may be more risky for people with cardiovascular disease, low blood pressure, kidney disease, problems regulating fluids, diabetes, reduced mobility, neurological conditions, a history of fainting or significant frailty. These are examples, not a complete contraindication list.

Some medicines can also affect sweating, blood pressure, hydration or kidney function. Anyone considering deliberate heat exposure who has relevant medical conditions or takes multiple medicines should discuss it with an appropriate healthcare professional first.

Do not stop or alter prescribed medication because of a hot-weather article. If you are unsure how a medicine may affect heat tolerance, ask your prescriber or pharmacist before hot weather arrives.

Hot-weather safety comes first

During hot weather, the safer improvements are familiar rather than exotic:

• drink enough fluid unless you have been medically advised to restrict fluids;
• keep living spaces cooler where possible;
• avoid excessive physical exertion during the hottest part of the day;
• use shade and wear suitable, loose clothing;
• check on vulnerable relatives, friends and neighbours; and
• pay attention to how you feel rather than waiting for a wearable to tell you that something is wrong.

There is no universal fluid target that is right for everybody. If you have heart or kidney disease, or have been told to limit fluids, follow the advice of your healthcare team. The GOV.UK Beat the Heat guidance and NHS hot-weather advice should take priority during an actual heatwave.

Heat exhaustion and heatstroke

If someone has heat exhaustion, move them to a cool place, remove unnecessary clothing, give them fluids and cool their skin with cool water and fanning. Stay with them. They should start to feel better within 30 minutes.

Get help from NHS 111 if symptoms are difficult to treat or you need advice. Heatstroke is a medical emergency: call 999 if someone remains unwell after 30 minutes of cooling and fluids, or has signs such as confusion, lack of coordination, a seizure, loss of consciousness or hot skin without sweating. Follow the current NHS heat exhaustion and heatstroke guidance.

Should you take hot baths before a heatwave?

Not as a general Age Watchers recommendation — yet.

The research is intriguing, but important questions remain:

• What is the minimum effective temperature?
• How long does exposure need to last?
• How often would it need to happen?
• How safe is it across different health conditions and medicines?
• Would a laboratory change meaningfully reduce illness during a real heatwave?
• How long would any acclimation last?

Until larger studies establish safer and practical protocols, deliberate prolonged hot-water immersion should not become another longevity challenge people copy from the internet.

Natural acclimatisation is real

When weather gradually becomes warmer, the body can naturally adapt over several days. The first very hot spell of the year can therefore be particularly challenging because people may not yet be acclimatised.

Where safe and comfortable, spending some time outdoors during progressively warmer weather may allow natural acclimatisation, while still following public-health guidance. This does not mean sitting in dangerous heat, exercising through symptoms or ignoring a heat-health alert.

Fitness may help too

Appropriate aerobic fitness can support cardiovascular function and heat tolerance, while regular physical activity supports healthy ageing more broadly. But do not deliberately perform strenuous exercise in extreme heat to “train” heat tolerance. During heat alerts, follow UK public-health advice and move activity to a cooler time or place.

Apply the Age Watchers framework

What about saunas?

Sauna exposure is also being researched for cardiovascular and heat-adaptation effects. Sauna temperatures are much higher than hot-bath temperatures, and the physiological stress can be significant.

Observational associations do not prove longevity benefits, and sauna use is not suitable for everyone. It should not be treated as a heatwave-preparation treatment. This is an area for a separate evidence review.

Climate resilience is becoming part of healthy ageing

Healthy ageing has traditionally focused on exercise, food, sleep, blood pressure and strength. But the environment matters too.

Future healthspan planning may increasingly include heat, air quality, housing, access to cooling, mobility during extreme weather and community support. Healthspan does not exist independently from the environment people live in.

Respect the heat

The encouraging finding is not that scientists have discovered a magic anti-heat bath. They have not.

It is that older bodies in these small studies retained the ability to adapt physiologically to repeated heat exposure. That tells us something important: ageing does not mean the body has stopped responding to training.

But until larger studies establish safer, practical protocols, deliberate extreme heat exposure should not become another longevity challenge to copy blindly.

For now: stay active, acclimatise sensibly, prepare for hot weather, know your risks and respect the heat.

MEASURE.
UNDERSTAND.
IMPROVE.
MAINTAIN.

Related reading

• How Well Are You Really Ageing?
• Can Chronic Stress Make Us Age Faster?
• The Sleep Pillar: Your Nightly Recovery Window
• What Is Healthspan?

Sources / Further reading

• Deshayes et al., 2026, The Journal of Physiology: heat acclimation and neural control of body temperature in older adults.
• 2026, Healthcare: four days of passive heat acclimation and exercise capacity in healthy older adults living in the UK.
• Cole et al., 2023: systematic review of short-term heat-acclimation protocols for an ageing population.
• Waldock et al., 2021: exercise heat acclimation and post-exercise hot-water immersion in older adults.
• GOV.UK: Beat the Heat — staying safe in hot weather.
• NHS: heat exhaustion and heatstroke.
• NHS: how to cope in hot weather.
• UKHSA: heat-health alerts.
• Met Office: Heat-Health Alert service.