How To Sleep In A Heatwave: 11 Science-Backed Ways To Stay Cool And Sleep Better Without Air Con

The UK spends most of the year wishing for warmer weather, then a heatwave arrives and we remember we're not particularly good at dealing with it.

This summer has brought heatwave after heatwave, with England recording its hottest June on record and temperatures climbing above 35°C. During the day, it's easy to see why people love it. Lunch breaks get longer, everyone finds an excuse to sit outside, the evening stretches on, and people generally seem to be in a better mood. But the nights? Not so much.

British homes are built to retain heat; a welcome feature in January, but in the middle of a heatwave, that smart architecture feels more like a design flaw. Brick walls absorb warmth throughout the day and release it slowly overnight, keeping our bedrooms uncomfortably warm. Unlike many homes in southern Europe, air conditioning is still a rarity in the UK.

A sweaty, restless night's sleep is about far more than feeling tired the next day. A few disrupted nights can quickly leave you feeling flat, foggy, and less like yourself. Anyone who has experienced a hot spell in the UK knows the pattern: you go to bed exhausted but can't properly switch off, the cool side of the pillow lasts about 30 seconds, the windows are open and the fan is working overtime yet you're still lying awake wondering why you feel so alert.

When we can't sleep in the heat, most of us blame the bedroom. Sleep experts tend to look at the body instead. Some of the most effective strategies involve helping the body release heat more efficiently while avoiding the common habits that keep core temperature elevated late into the evening, according to sleep physiologist Stephanie Romiszewski, MSc, and functional medicine practitioner Rose Ferguson, MSc Adv Nut.

Before getting into what works, it helps to understand what heat is actually doing to sleep in the first place.

Why heat makes it harder to sleep

"Sleep isn't something we do. It's something our brain allows to happen,” says Romiszewski. "One of the signals that helps kickstart sleep is a small drop in core body temperature, but in a heatwave, that process becomes less efficient."

In the hours before bed, the body starts moving heat away from its core and towards the skin. That gradual cooling process forms part of the circadian rhythm and helps create the conditions needed for sleep. A heatwave makes that job a lot harder.

Your brain may be ready for sleep, but your body is still trying to get rid of excess heat. Rather than preventing sleep altogether, hot nights usually make sleep lighter and more fragmented. You may wake more frequently, spend more time awake during the night, and feel less refreshed the following morning. While that can be frustrating, it doesn't mean you've suddenly become a bad sleeper. Your body is attempting to carry out one of its most temperature-sensitive processes in a bedroom that's still holding onto the day's heat.

Most people can't retrofit air conditioning halfway through a heatwave, but you can help your body cool down more effectively. The strategies below focus on reducing heat load and improving heat loss, giving your body the best chance to cool itself before sleep.

1. Hydrate throughout the day, not at bedtime

After a busy day, people realise they've barely had anything to drink and attempt to catch up by drinking large amounts of water in the evening. Ferguson says this approach often creates a new problem. "A litre of water at 10pm mostly guarantees you will be up at 3am for the loo," she says.

Once you're awake, getting back to sleep in a hot bedroom can be difficult. Hydration also influences thermoregulation, the process your body uses to maintain a stable internal temperature. Sweating is the body's main cooling mechanism, allowing heat to escape as moisture evaporates from the skin. When fluid intake is too low, that cooling system becomes less effective.

What to do: Aim to drink the majority of your fluids before 6pm. As a rough guide, aim for around 2 litres on a typical day and closer to 2.5–3 litres during a heatwave, especially if you’re exercising, commuting in the heat or spending lots of time outside. 

If you're thirsty after dinner, take small sips rather than gulping multiple glasses before bed. Urine colour can also provide a useful guide. If your pee is the colour of pale straw, generally that suggests adequate hydration, while dark yellow usually means you needed more fluid earlier in the day.

2. Drink electrolytes when you've genuinely lost salts

Electrolytes seem to be the drink everyone is sipping right now. Whilst they certainly have their place, not everyone needs them every day. According to Ferguson, electrolytes are most useful when you've lost substantial amounts of fluid and minerals through sweating. Sweat contains sodium, potassium, and other electrolytes, alongside water. During a heatwave, losses can accumulate surprisingly quickly, particularly if you've exercised outdoors, spent hours in the sun, or found yourself waking up to damp sheets after a hot night.

Replacing fluid without replacing those minerals can sometimes leave people feeling flat, headachy, or prone to muscle cramps. "Water alone in those situations can dilute sodium further, which leaves you feeling worse, not better," says Ferguson.

What to do: Consider an electrolyte drink earlier in the day if you’ve:

• Trained in the heat
• Spent several hours outdoors
• Sweated heavily
• Experienced muscle cramps
• Developed a heat-related headache

When choosing an electrolyte, look for one that contains roughly 300–700mg of sodium per serving. Sodium is the mineral lost in the greatest quantities through sweat and helps the body retain and distribute fluid more effectively. Without enough sodium, a drink may taste the part but do little to replace what has actually been lost during a hot day.

Like the rest of your fluid intake, try to drink electrolytes during the day rather than immediately before bed. The aim is to replace losses before they start affecting sleep, not create another reason to wake up during the night.

3. Eat dinner at least three hours before bed

"Digestion is thermogenic, meaning it literally raises body heat, so a large late meal will not help the heat situation," says Ferguson.

Every meal generates heat as your body breaks down, absorbs and processes nutrients. Scientists call this the thermic effect of food. Depending on what you've eaten, digestion accounts for around 10% of your daily energy expenditure, and that energy is released as heat.

On a cool evening, you'd barely notice. But during a heatwave, it can be the difference between starting to cool down before bed and still feeling like your body's running warm when your head hits the pillow.

What to do: Try to finish dinner around three hours before bed. If that isn't realistic, avoid large, heavy meals late in the evening where you can. A lighter dinner generates less metabolic heat than a big meal eaten just before climbing into bed.

4. Don't mistake alcohol for a sleep aid

Few heatwave rituals feel more appealing than a cold drink in the evening but the problem is that alcohol works against several of the processes that help us stay cool and sleep well. "A cold glass of rosé in the garden feels like the answer to a heatwave. Physiologically, it's the opposite," says Ferguson.

Alcohol increases fluid loss, raises heart rate, disrupts temperature regulation, and suppresses REM sleep, the stage associated with learning, memory, and emotional processing.

While alcohol may make you feel sleepy initially, research consistently shows it fragments the second half of the night. People tend to wake more frequently, spend longer awake once they do, and report poorer sleep quality overall. During a heatwave, those effects can become even more noticeable. A body that's already working hard to regulate temperature is given another challenge to deal with.

What to do: If you're drinking alcohol, keep it to one or two drinks, alternate alcoholic drinks with water, and try to finish drinking at least three hours before bed.

5. Schedule workouts for the morning or lunchtime

A hard workout doesn't stop when you finish exercising. Core body temperature can rise by more than 1°C, heart rate stays elevated, and your body continues generating heat as it repairs and recovers.

Recovery is an active process. It takes energy to repair muscle, restore fuel stores and bring the body back to its resting state. All of that generates heat. During a heatwave, that leaves your body with more work to do before sleep can begin.

What to do: You don't need to stop exercising just because it's hot. However, if you can, save harder sessions for the morning or lunchtime, when the temperature is lower. In the evening, opt for a walk, mobility work, or some gentle stretching instead. That way, you're winding your body down rather than asking it to lose even more heat before bed.

6. Cool your hands and feet before your forehead

Most of us instinctively reach for a cold flannel on our forehead, but Romiszewski suggests starting somewhere else. "The hands and feet are particularly good at getting rid of heat, so cooling them can help your body cool down more effectively," she says.

Your palms and the soles of your feet contain specialised blood vessels that sit close to the skin's surface. They're some of the easiest places for your body to transfer heat into the surrounding air, making them surprisingly effective targets before bed. Think of them as your body's built-in radiators. You're not trying to make yourself cold. You're giving your body an easier route to lose heat before you get into bed.

What to do: You don't need ice baths or expensive cooling gadgets. Run cool water over your hands, wrists, and feet for 60–90 seconds before bed. You could also try a cool foot bath while you're reading, wrap a damp flannel around your wrists, or place a cool water bottle near your feet. 

7. Take a cool shower, not an ice-cold one

"Very cold water can be quite stimulating and may even make it harder for your body to get rid of heat afterwards," says Romiszewski. After a hot, sticky day, a freezing shower sounds like exactly what you need, but your body sees it differently. Very cold water causes blood vessels near the skin to narrow, making it harder to shift heat from your core to your body's surface. The sudden cold can also leave you feeling more alert, which isn't ideal when you're trying to drift off.

A cool or lukewarm shower works with your body's natural cooling process instead of against it. It takes the edge off without triggering those same heat-conserving responses, allowing your body to keep releasing heat as bedtime approaches.

What to do: Take a cool shower around 30–60 minutes before bed. The water should feel refreshing, not painful. If you're gasping when it hits your skin or counting down the seconds until it's over, it's probably colder than it needs to be. The aim isn't to shock your body into feeling cold. It's to give it a helping hand to naturally cool down before sleep.

8. Keep your bedroom cool by blocking the day’s heat 

"Take a lesson from the dog," says Romiszewski. "They always seem to find the coolest patch of floor in the house." By the time you climb into bed, the damage has often already been done. There's only so much a fan can do. It might make you feel cooler, but it can't get rid of the heat that's been building up in your bedroom all day.

That's because sunlight doesn't just warm the air. It heats your walls, floors and furniture throughout the day, and they slowly release that heat back into the room even after sunset. It's why your bedroom can still feel stuffy at 10pm, despite the temperature outside starting to cool off. 

What to do: Keep curtains, blinds or shutters closed during the hottest part of the day, especially if your bedroom gets strong afternoon sun. Once it feels cooler outside than it does indoors, throw the windows open. If you can, open windows on opposite sides of your home to create a through-draught and help flush some of that trapped heat out.

9. Don't expect your best night's sleep

A heatwave isn't the time to chase perfect sleep. Sleep may be lighter than usual. You may wake more often or spend a little longer awake during the night. That doesn't necessarily mean you've become a bad sleeper. It's a normal response when your body is working harder to lose heat. "We often treat a hot night as a problem to solve, when really it's something to get through," says Romiszewski.

Checking the time, analysing your sleep score, or working out how exhausted you'll feel tomorrow can shift your attention away from resting and towards monitoring. Ironically, that's when it often becomes harder to fall back asleep. Sleep is one of the few biological processes that doesn't respond well to being controlled. You can create the right conditions for it, but you can't force it to happen.

What to do: If you wake during the night, resist the urge to check the time. Instead of focusing on whether you're asleep, focus on resting instead. Even if you don't drift off straight away, lying quietly with your eyes closed still gives your brain and body a chance to switch down a gear.

If your mind is racing, try a short NSDR (Non-Sleep Deep Rest) session. It's not designed to make you fall asleep but it helps reduce mental and physical arousal, making it easier for sleep to return naturally if you're ready for it.

The next morning, get outside for some daylight and stick to your usual wake-up time if you can. One unsettled night during a heatwave is unlikely to have much lasting effect. The bigger disruption usually comes from changing your routine or worrying that you've ruined your sleep.

10. Choose bedding and sleepwear that keep you cool

Thick duvets and heavy fabrics trap warmth around your body, making hot nights feel even hotter and increasing the chances you'll wake during the night.

What to do: Pack away the winter bedding for a start. During a heatwave, a 2.5–4.5 tog duvet is usually a better choice than the 10.5–13.5 tog duvets many of us use for most of the year. If it's particularly warm, a flat sheet or even no duvet at all may be all you need.

Choose breathable natural fabrics where you can. Cotton and linen allow air to circulate more freely than many synthetic materials, making them a better choice for hot, sticky nights. The same goes for sleepwear. Loose-fitting, lightweight pyjamas or a cotton T-shirt and shorts are generally cooler than heavier fabrics or anything tight-fitting.

What about sleeping naked? It might seem like the coolest option, but if you sweat during the night, lightweight, breathable sleepwear can actually leave you feeling drier by wicking moisture away instead of letting it sit against your skin.

11. Consider a magnesium or glycine supplement

No supplement can compensate for a bedroom that feels like a greenhouse, but if you've already addressed hydration, meal timing and cooling strategies, magnesium or glycine may be worth considering.

Magnesium supports normal nervous system function and muscle relaxation. It isn't a sleeping pill, but some evidence suggests people with lower magnesium levels may notice improvements in sleep quality when they supplement.

Glycine works differently. Research suggests it can produce a small reduction in body temperature while improving subjective sleep quality. That makes it particularly interesting during a heatwave, when cooling down is one of the biggest barriers to falling asleep.

Can you take both?

Yes. Magnesium and glycine work in different ways, so they're often taken together rather than instead of one another.

What to do: Ferguson recommends magnesium bisglycinate, a form that's generally well absorbed and often better tolerated than other forms of magnesium. She typically suggests 200–400mg around one to two hours before bed. Studies on glycine have generally used 3g taken around one hour before bedtime.

Think of supplements as an extra rather than a shortcut. If your bedroom is still retaining the day's heat, changes to your routine and sleeping environment will almost always have a bigger impact than adding another capsule or powder.

A better way to think about sleeping in a heatwave

Most of us spend a hot night trying to cool the bedroom. Sleep experts spend more time thinking about how to help the body lose heat. It turns out those are two different things. The room might still be warm, but you can make it easier for your body to release heat before bed. That's the thinking behind every tip in this guide.

Some nights will still be warmer than you'd like. That's part of a British heatwave. But when you work with your biology instead of fighting it, getting to sleep becomes a whole lot easier.

Your sleep in a heatwave questions, answered

Why can't I sleep when it's hot?

Falling asleep depends on a small drop in your core body temperature. A warm bedroom makes that harder, so sleep becomes lighter and more broken – you wake more often and feel less refreshed. It doesn't mean you've become a bad sleeper.

How do I keep my bedroom cool in a heatwave?

Close curtains, blinds or shutters during the hottest part of the day to stop sunlight heating your walls and furniture. Once it's cooler outside than in, open windows on opposite sides of the home to create a through-draught.

Should you sleep naked in a heatwave?

Not necessarily. If you sweat overnight, lightweight breathable sleepwear in cotton or linen wicks moisture away and can leave you drier than sleeping naked.

Do I need electrolytes in a heatwave?

Only when you've genuinely lost fluid and salts – after training in the heat, hours outdoors, heavy sweating or a heat headache. Choose a drink with 300–700mg of sodium per serving and take it during the day, not before bed.

Can you take magnesium and glycine together for sleep?

Yes. They work differently, so they're often combined – magnesium bisglycinate (200–400mg) one to two hours before bed, and glycine (around 3g) roughly an hour before.

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