How to Stay Cool in a Heatwave

UK homes are built to trap heat, not release it, and most of us are improvising when temperatures climb. Here's what actually works to stay cool in a heatwave — including a few things most people get wrong.

The UK is not built for heat. Homes designed to retain warmth through long grey winters become ovens in summer, air conditioning remains rare, and the practical knowledge that hotter countries take for granted is something most British households are still acquiring in real time. This matters more each year: Met Office research now puts the likelihood of exceeding 40°C at more than 20 times what it was in the 1960s, and heatwaves are becoming longer as well as more frequent.

Staying cool is not just a comfort question. During heatwaves, more people than usual become seriously ill or die, and most of that harm is preventable with the right actions. Here is what genuinely works — and the handful of common moves that quietly make things worse.

TL;DR

Keep the heat out before it gets in: close windows, curtains, and blinds during the day, and open them only when the air outside has cooled, usually at night. Opening windows during the hottest part of the day can make a room hotter, not cooler.

Electric fans help — but only below around 35°C. Above that, moving hot air over the skin stops cooling you and can accelerate dehydration. Don't aim a fan directly at your body for long periods.

Stay hydrated with water and limit alcohol, which dehydrates and impairs temperature regulation. Eat cold, water-rich foods, and replace the salts lost through sweat with a balanced diet.

Cool the body directly: a cool — not cold — shower, a damp cloth on the wrists and neck, and cold water on the pulse points work better than you'd expect. Cold showers can be counterproductive.

Avoid the hottest hours: stay out of direct sun between 11am and 3pm, and shift exercise, dog walks, and any physical activity to early morning or evening.

At night, sleep in the coolest part of the home, turn off and unplug heat-generating electronics, and use light bedding. Heat rises, so a lower floor is usually cooler.

Check on those most at risk — older people, those living alone, people with heart, breathing, or kidney conditions, and young children — who are far more vulnerable to heat.

Keep the Heat Out of Your Home

The single most important principle of keeping a home cool is also the most counterintuitive: for most of the day, you want the windows closed.

It feels natural to throw the windows open when a room gets hot. But if the air outside is hotter than the air inside — which it is during the hottest part of the day — opening the windows simply lets that hotter air in. The better approach is to close windows, curtains, and blinds during the day to keep the warm air and direct sun out, and then open the windows at night once the outside temperature has dropped below the inside temperature. When you do open them, opening windows on different sides of the home creates a through-draught that moves air far more effectively than a single open window.

External shading beats internal shading, because it stops the sun's heat before it passes through the glass, but curtains and blinds still make a meaningful difference, particularly on south- and west-facing windows. Reducing the heat generated inside the home helps too: turn off lights and electrical equipment not in use, and cook at cooler times of the day, since an oven or hob adds significant heat to a room.

When a Fan Helps — and When It Doesn't

Electric fans are the default cooling tool in most UK homes, and for most of a heatwave they work well. But there is a specific limit worth knowing.

Below around 35°C, a fan helps by moving air across the skin and accelerating the evaporation of sweat, which is how the body sheds heat. Above roughly 35°C, this stops working. The air is now hotter than your skin, so the fan is essentially blowing hot air over you, which no longer cools you and can speed up dehydration by increasing sweat loss without a corresponding cooling benefit. In very high temperatures, a fan can give a false sense of safety.

Official NHS guidance is also not to aim a fan directly at your body for prolonged periods, for the same dehydration reason. A fan positioned to circulate air around the room is more useful than one pointed straight at you. Placing a bowl of ice in front of a fan, an old trick, does produce a brief cooling mist effect but makes little difference over time.

Cool the Body Directly

When you need to bring your own temperature down, the most effective methods target the points where blood flows close to the skin.

A cool shower or bath is one of the most reliable ways to lower body temperature. The important detail is cool, not cold: a freezing-cold shower causes blood vessels at the skin's surface to constrict, which can trap heat in the body's core and produce a rebound warming effect, the opposite of what you want. Tepid or cool water is more effective for sustained cooling. Running cold water over the wrists, splashing the face, or pressing a damp cloth to the neck, wrists, and the pulse points cools the blood passing close to the surface and is a quick, low-effort way to take the edge off.

Cold, water-rich foods do double duty, providing hydration and a cooling effect: ice lollies, chilled fruit, salads, cold soups, and yoghurt. This also aligns with the body's natural tendency to want lighter, cooler food in the heat.

Hydration and What to Drink

Sweating is the body's primary cooling mechanism, and in a heatwave you lose fluid and salts faster than usual, so replacing them matters. Electrolytes become particularly relevant in sustained heat, since plain water alone does not replace what is lost through heavy sweating.

Drink plenty of fluids across the day rather than waiting until you feel thirsty, since thirst lags behind actual need. Water, diluted squash, and fruit juice are all good options. A balanced diet helps replace the salts lost through sweat, which is why eating normally — and including some salt — matters even when the heat suppresses appetite.

Alcohol works directly against you in the heat. It is a diuretic, increasing fluid loss through urine, and it impairs the body's ability to regulate its own temperature. The instinct to cool off with a cold beer or a glass of wine in the sun is understandable, but limiting alcohol is one of the more impactful single choices for staying safe in a heatwave. The same caution applies, to a lesser degree, to large amounts of caffeine.

Avoid the Hottest Hours

The sun is at its strongest, and UV levels highest, between 11am and 3pm. Staying in the shade during these hours is the simplest way to avoid the worst of the heat.

Any physical activity — exercise, walking the dog, gardening, manual work — is best shifted to the early morning or the evening, when temperatures are lower. Pushing through a workout in the midday heat of a heatwave is one of the more common ways otherwise healthy people end up with heat exhaustion. If you must be out in the sun, wear lightweight, loose-fitting, light-coloured clothing, a wide-brimmed hat, and sunscreen of at least SPF 30, and carry water.

A note on water: open water — rivers, lakes, reservoirs, the sea — is a tempting way to cool off and a genuine danger in hot weather. Open water is often far colder than it looks, which can trigger cold water shock, and summer sees a marked rise in drowning accidents. The cooling effect of the water also masks UV exposure, so sunburn happens faster than expected.

Staying Cool at Night

Sleep is harder in the heat, and quality sleep is exactly what the body needs to recover and regulate its temperature during a heatwave, so it is worth protecting. We've written a full guide to sleeping in a heatwave covering the biology and the most effective interventions in detail.

Heat rises, so the lowest floor of a home is usually the coolest place to sleep; if the home is on one level, move to its coolest room. Electronics generate heat even on standby, so turn off and unplug anything in the bedroom that isn't needed. Light, breathable bedding and nightwear — or none — help, as does a cool shower before bed to lower your core temperature going into sleep. Keeping a glass of water by the bed and a damp cloth to hand covers the rest.

Look Out for Those Most at Risk

Heat does not affect everyone equally, and the people most vulnerable to it are often the least able to take action themselves.

Those at higher risk include older people, people who live alone, those with serious long-term conditions — heart problems, breathing problems, diabetes, kidney disease, dementia — people on multiple medications, and babies and young children. During a heatwave, checking in on elderly or unwell relatives, friends, and neighbours is genuinely one of the most useful things anyone can do. Make sure they are drinking enough, that their living space is as cool as it can be, and that they know the signs of heat exhaustion.

Knowing those signs matters for everyone. Heat exhaustion — heavy sweating, tiredness, dizziness, nausea, headache — should improve within 30 minutes of cooling down and resting. If it does not, or if someone shows signs of heatstroke — confusion, a very high temperature, hot dry skin, loss of consciousness — that is a medical emergency: call 999 immediately and cool the person while you wait.

Frequently Asked Questions

Should I open my windows during a heatwave? Not during the hottest part of the day. If the air outside is hotter than the air inside, opening windows lets hot air in and makes a room warmer. Keep windows, curtains, and blinds closed during the day to keep heat out, and open windows at night once the outside air has cooled. Opening windows on opposite sides of the home then creates a cooling through-draught.

Do fans actually help in a heatwave? Yes, but only below around 35°C. Below that, fans help sweat evaporate and cool the skin. Above roughly 35°C, the air is hotter than your skin, so a fan blows hot air over you without cooling and can speed up dehydration. Don't aim a fan directly at your body for long periods.

What's the best way to cool down quickly? Target the pulse points where blood runs close to the skin: run cool water over your wrists, splash your face, or press a damp cloth to your neck and wrists. A cool — not cold — shower is very effective. Avoid freezing-cold showers, which can constrict blood vessels and trap heat in the core. Cold, water-rich foods like ice lollies and chilled fruit help too.

What should I drink in a heatwave? Plenty of water across the day, plus diluted squash or fruit juice. Eat a balanced diet to replace the salts lost through sweat. Limit alcohol, which dehydrates you and impairs your body's temperature regulation, and go easy on large amounts of caffeine. Don't wait until you feel thirsty to drink, as thirst lags behind your body's actual needs.

How can I sleep when it's too hot? Sleep in the coolest part of your home — a lower floor if you have one, since heat rises. Turn off and unplug electronics in the bedroom, as they generate heat even on standby. Use light bedding, take a cool shower before bed, and keep water and a damp cloth nearby. Open the bedroom window at night only if the air outside has become cooler than inside.

Who is most at risk in hot weather? Older people, those living alone, people with serious conditions such as heart, breathing, or kidney problems, diabetes or dementia, people on multiple medications, and babies and young children. These groups are far more vulnerable to heat, so check on them during a heatwave — make sure they're hydrated, their home is cool, and they know the signs of heat exhaustion.

The Bottom Line

Staying cool in a heatwave is mostly about getting a few principles right and avoiding a few common mistakes. Keep the heat out of your home during the day and let the cool in at night. Use fans wisely, and know when they stop helping. Cool your body at the pulse points with cool rather than cold water. Hydrate steadily, limit alcohol, and stay out of the midday sun. Sleep low and dark. And check on the people around you who are most at risk.

None of it is complicated, but in a country still adjusting to summers it was never built for, knowing the difference between what works and what merely feels right is increasingly worth having.

The Sleep Reset and Stress Reset guides pair well with Reset Companion for the recovery work that hot weeks tend to demand — restoring the sleep, hydration, and nervous-system balance that a heatwave erodes.

This is a sensitive area, and if you or someone you're worried about is struggling in the heat or showing signs of heat exhaustion or heatstroke, the NHS (111 for advice, 999 in an emergency) can help.

Related reading: Electrolytes: Why Water Alone Isn't Enough in the Heat · How to Sleep in a Heatwave · Heat Exhaustion vs Heatstroke · Your Gut Doesn't Travel Well. Here's What You Can Do About It.

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