To sleep when it's hot in a home without air conditioning, you need to do three things: stop the heat getting into the bedroom during the day, get the air moving in the evening and overnight, and cool your body directly with light bedding, a lukewarm shower and a fan on your skin. Most of the gain comes from the first one, and it happens hours before bedtime.
That is the answer. The rest of this guide goes through each part in the order you would do it on a hot day, because timing matters more than any single gadget.
Why UK homes are so bad at this
British houses and flats are built to keep heat in. Thick walls, small windows, loft insulation and double glazing are all designed for January. In a heatwave, the same features turn the building into a storage heater: the fabric of the house warms up over several days and then radiates heat back into the rooms at night, which is why the third night of a hot spell is often worse than the first even when the outside temperature is the same.
Top-floor flats and rooms under the roof are hardest hit. So are bedrooms facing south or west, which get the afternoon sun.
The problem for sleep is that your core temperature needs to fall by a degree or so for sleep to come. In a bedroom at 26°C under a duvet, it cannot. Research by Obradovich and colleagues (2017), using data from tens of thousands of people, found that unusually warm nights were linked to measurably more reports of poor sleep, with the effect strongest in summer. Anyone who has tried to sleep through a British heatwave will not be surprised.
In short: You cannot chill the room, so stop it heating up in the first place, move air at night, and cool your skin rather than the air.
During the day: keep the heat out
This is the part people get backwards. The instinct is to open everything on a hot day, but while the air outside is hotter than the air inside, an open window is heating your bedroom.
- Close blinds and curtains on the sunny side from mid-morning. Pale or reflective backings work best; thermal blackout curtains, sold for winter warmth, do the same job in reverse in summer. A blind between the glass and the curtain is better still.
- Close windows on the sunny side while the outside is hotter than the inside. Open them on the shaded side if there is a breeze.
- Keep internal doors open so air can move through the flat, unless one room is much hotter than the rest, in which case shut that one off.
- Do not add heat. Ovens, tumble dryers, dishwashers and a laptop left running on the bed all warm the room. Cook early or cook cold.
- Switch off standby devices in the bedroom. Each one gives off a little heat.
If you are out at work all day, do this before you leave. A closed, shaded bedroom at 6pm can be several degrees cooler than an open one.
Evening: let the cool in and get air moving
Once the outside air is cooler than the inside, usually from about 8pm or 9pm onwards, open everything.
Cross-ventilation is the aim: windows open on opposite sides of the home, with internal doors propped, so that air flows through. If you have windows on only one side, open the top and bottom of a sash window, or two windows in the same wall, to get some circulation.
Fans do not cool the air, but they do two useful things. A fan in a window, blowing out, pulls hot air from the room and draws cooler air in through other openings. A fan pointed at you moves air across your skin so that sweat evaporates, which is how your body actually cools itself. A quiet fan matters at night; a rattling one becomes its own problem, and it is worth checking what other noise an open window lets in.
The ice bowl trick is real but modest. A bowl of ice or a frozen bottle in front of a fan cools the air passing over it for an hour or so. It will not chill a room, but it can make the first stretch of the night more comfortable.
Bedding: swap it, do not just throw it off
A 10.5 tog duvet is the wrong tool in July. Options, from lightest upwards:
- A sheet only. A cotton or linen flat sheet over you is often enough on the hottest nights.
- A summer duvet of around 4.5 tog, or the lighter half of an all-seasons duvet. Some people sleep better with a light covering than with nothing, because it stops the skin cooling too far in the early hours.
- Breathable fabrics. Cotton percale is crisp and cool-feeling; linen wicks well and gets softer with washing. Polyester and microfibre sheets trap heat and sweat. Check the label: "easy care" often means a polyester blend.
- The pillow. Your head loses a lot of heat, and a hot pillow is a common reason for waking. Turning it over helps for a few minutes. A pillow with a cooling gel layer, or a breathable cover, helps for longer.
- The mattress. Memory foam holds heat. If you sleep on foam, a cotton topper or a mattress protector that breathes makes a noticeable difference.
There is a fuller run-through of togs and fabrics in the bedding and sleep guide, and a specific one for cooling pillows.
The three things most people end up buying
A quiet fan for the air, a lighter duvet for the bed and a cooler pillow for the head. In that order of impact, for most homes.
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Quiet bedroom fan
Example: Various (pedestal or desk fans marketed as quiet or with a night mode)
Bedroom fans marketed as 'quiet' typically advertise low decibel levels at their lowest settings and often include a timer. A fan moves air rather than cooling it, so it helps most when air can also be exchanged with a cooler room or outside.
- Best for
- Hot nights in homes without air conditioning
- Key feature
- Low noise at low speeds, timer or night mode
- Why it may help
- Airflow over the skin helps sweat evaporate, which is how the body cools. A fan also produces steady sound that masks other noise.
- Worth knowing
- Noise levels are self-reported by manufacturers; in very hot, humid rooms a fan alone has limited effect.
Lightweight summer duvet (around 4.5 tog)
Example: Various UK brands
Tog is the UK measure of a duvet's warmth. Duvets around 4.5 tog are marketed as summer weight; all-season sets combine a summer and a mid-weight duvet that clip together for winter.
- Best for
- Hot sleepers and UK summers
- Key feature
- Low tog rating for minimal insulation
- Why it may help
- Swapping a 13.5 tog winter duvet for a summer weight one is one of the simplest ways to stop waking up hot.
- Worth knowing
- Fill (down, feather, microfibre, wool) affects breathability as much as tog.
Gel-layer cooling pillow
Example: Various (gel-topped memory foam)
Cooling pillows commonly combine memory foam with a gel layer or gel-infused foam, and are marketed as feeling cooler to the touch. The cooling effect is usually most noticeable at first contact rather than all night.
- Best for
- Hot sleepers who like foam support
- Key feature
- Gel-infused or gel-layered foam marketed to draw heat away from the head
- Why it may help
- If you wake up hot, the pillow is one of the warmest contact points. A breathable or gel-layered pillow paired with a cool room can help.
- Worth knowing
- Cooling claims vary and are hard to compare; a breathable cover and cool room matter as much as the pillow itself.
Cooling yourself, not the room
Shower lukewarm, not cold. A cold shower feels wonderful for a minute, but the shock makes your body constrict blood vessels near the skin and hold heat in. A lukewarm or cool shower, ten to twenty minutes before bed, lowers skin temperature gently and lets the heat loss continue after you get out.
Cool the pulse points. Running cold water over your wrists and forearms, or holding a cold flannel to the back of the neck, cools blood close to the surface. Damp socks in the freezer for ten minutes is a popular trick; it feels strange and works surprisingly well.
Drink water through the evening, and keep a glass by the bed. You lose a lot of fluid sweating overnight, and mild dehydration makes you feel hotter and wake more. Go easy on alcohol: it feels cooling, but it disrupts sleep in the second half of the night and leaves you more dehydrated.
Sleep lower. Heat rises. If you have the option, a mattress on the floor or a downstairs sofa on the hottest nights can be several degrees cooler than a bed upstairs. This is not a defeat; it is what people in hot countries have always done.
Sleep apart. Two bodies in one bed generate a lot of heat. On the worst nights, separate beds or separate rooms are entirely reasonable.
Light and the early wake
Hot weather in the UK arrives with long days, and by 4:30am in June the sky is light. Combine that with a warm room and you have the classic summer pattern: asleep by midnight, wide awake at 4:15 and hot. Dealing with the light matters as much as the heat. The guide to making your bedroom darker covers blackout options and masks; a thermal blackout blind does both jobs at once.
Who needs to be careful
Hot nights are uncomfortable for most people and a genuine risk for a few. Babies and small children, people over 65, and anyone with heart, lung or kidney conditions or taking medication that affects how the body handles heat should follow the NHS heatwave guidance and check on each other. Symptoms such as headache, dizziness, nausea, confusion or a fast pulse that do not settle in a cool place within half an hour need medical advice: call 111, or 999 if someone becomes confused or unresponsive.
Tonight's version
Close blinds and windows on the sunny side now, open everything once it is cooler outside, put a fan where it will blow over you, and get into bed under a sheet after a lukewarm shower with a glass of water beside you. If you still wake hot at 4am, that is the heat and the light together rather than anything wrong with you; the guide to waking up hot at night covers what to do in the moment.
For the cooler months, the best temperature for sleep guide explains why a cool room helps all year, and the rest of the Sleep Environment guides cover light, noise and bedding.
Frequently asked questions
Should I sleep with the window open in a heatwave?
Yes, once the air outside is cooler than the air inside, which in a UK heatwave is usually from late evening onwards. During the day, while it is hotter outside than in, keep windows and blinds on the sunny side closed. Open windows on opposite sides of the flat if you can, to get air moving through.
Is it better to sleep naked when it's hot?
It depends on the person. Bare skin loses heat well, but sweat can then pool on the sheet and feel clammy. Many people find a loose, thin cotton or linen layer that wicks sweat away is more comfortable than nothing. Try both and go with whichever lets you settle.
Does a fan actually cool the room?
No. A fan does not lower the air temperature; it moves air across your skin so that sweat evaporates faster and you feel cooler. That is why it helps most when pointed at you, and why it does little in an empty room. In very hot, dry conditions above body temperature a fan can make things worse, but that is rare in the UK.
Why do I wake at 4am when it's hot?
Deep sleep is concentrated in the first half of the night. By the early hours sleep is lighter, and your body is also trying to keep its temperature down before the natural morning rise. Heat interferes with both, so waking hot and sticky at 3am or 4am is very common in a warm room.
Sources and further reading
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Written and reviewed by the Quiet Mind Sleep editorial team in line with our editorial policy. Spotted an error? Let us know.
