How to keep cool without air conditioning in a heatwave

Why this matters more every summer

Updated 30 October 2026

Europe's summer of 2026 was its third warmest on record, and western Europe's warmest ever, beating 2003, according to the EU's Copernicus climate service. The first big heatwave hit western Europe in late May. By the end of the season about half the continent, 52%, had reached "very strong" heat stress, meaning it felt like 38 °C or more.

In June the WHO's Europe office said heat had killed more than 200,000 people across the EU and its associated countries in just four years, and that most of those deaths were entirely preventable. Its advice for households was plain: blinds and curtains closed by day, windows open at night, drink before you are thirsty, stay out of the midday sun, and check on older neighbours and relatives. "A phone call costs nothing and can save a life."

None of that needs air conditioning. Here is how to do it well.

Keep the heat out of the house

A house heats up from the sun on its glass, walls and roof. Stop the sun before it gets in and you have won most of the fight.

• Shade outside the glass if you can. Shutters, an awning or an outside blind stop the heat before it reaches the window. Curtains and blinds inside still help; close them on every sunny window.
• Close the sunny side first. East-facing rooms in the morning, south and west in the afternoon. Shut them before the sun reaches them, not after the room is already hot.
• Shade the hot wall. A sheet, a sun sail or a tarp hung outside on the sunny side, with air behind it, keeps the sun off the wall itself.
• Switch off what makes heat. Ovens, tumble dryers, old bulbs, a computer left on. Cook once, early, and eat cold food later.
• Top-floor flats are the hottest homes in any city. Heat rises through the building and the roof bakes. If that is you, plan where you will spend the worst afternoons: a cooler room downstairs at a friend's, a library, a church, a shopping centre.

Open at night, shut by day

This is the opposite of what most people do. They open the windows at noon because the room feels stuffy, and the hot air pours in.

Do it the other way round. From an hour after sunset, when the air outside is cooler than the air inside, open everything you safely can, on both sides of the house, so air moves through. Leave it open until an hour or so after dawn. Then, as the day warms, shut the windows and draw the curtains and keep the night's cool in. Check the outdoor thermometer if you have one: when outside is hotter than inside, the windows stay shut.

Cool the body, not the room

When the house is hot anyway, work on the person.

• A wet cloth on the back of the neck or across the forehead cools you faster than anything except a cool shower. Re-wet it every half hour.
• Feet in a bowl of cool water while you sit. A damp T-shirt does the same over a bigger area.
• Sleep low. Hot air rises. A mattress on the floor of the coolest room beats the bed upstairs by a few degrees. A damp sheet over you, with a breeze, is the nearest thing to air conditioning without power.
• Light, loose, pale clothes, and a wide hat outside.
• Do the heavy jobs early and late. The NHS says stay in the shade between 11am and 3pm. Shopping, gardening, carrying and exercise go at the start and end of the day; in the middle of it, sit still in the coolest place you have.

About fans: a fan helps while the air is cooler than your skin, because it moves sweat off you. The NHS says electric fans can help when the temperature is below 35 °C (95 °F). Above that, and in a power cut when there is no fan anyway, water on the skin does the work.

Drink before you are thirsty

A cup of water every hour you are awake is my rule in a heatwave, and more if you are working or sweating hard. If you are sweating a lot for hours, a rehydration drink puts back the salt as well: the WHO sugar and salt recipe takes two minutes to make. The NHS says avoid alcohol, caffeine and hot drinks; the WHO adds sugary ones.

Older people feel thirst late, and children forget. Put a jug and a glass where they can see them and fill the glass yourself. If the power is off for long, your stored water goes faster in heat than in any other emergency; the water-per-person numbers are a floor in hot weather, not a ceiling.

Who gets into trouble first

Heat kills quietly, indoors. The classic case is an older person alone in a top-floor flat with the windows shut, not drinking because they are not thirsty, who slips into heatstroke over a day or two. The people most at risk:

• People aged 65 and over, especially those who live alone
• Babies and children aged 5 and under, and pregnant women
• Anyone with a serious long-term condition: heart or breathing problems, dementia, diabetes, kidney disease
• People taking several medicines, or medicines that make heat harder to handle (ask the pharmacist; don't stop taking them)
• Anyone already ill or dehydrated, anyone homeless, and anyone working outside or doing manual work

If you know someone on that list, call or knock twice a day while the heat lasts: once in the morning and once in the late afternoon, when the house is at its hottest. Check that the room they are in is cool, that there is water by the chair, and that they are drinking it. Never leave a child or an animal in a parked car, not for a minute.

Heat exhaustion or heatstroke?

Two stages of the same thing. The line between them is the line between a bad afternoon and an emergency.

The rule I teach: sweating and miserable, cool them and watch the clock. Hot, confused or not making sense, cool them and call for help. Don't give drinks to someone who is confused or not fully awake; they can choke.

This page is information, not medical advice. If you are worried about someone in the heat, call your doctor, NHS 111 in the UK, or the emergency number. The heat-illness signs follow the NHS and the WHO; the house-cooling advice is from the book.