the ideal temperature for sleep

the sleep summary:

• The ideal bedroom temperature for sleep is between 16 -18°C for most adults, according to The Sleep Charity and NHS guidance.

• Sleeping at temperatures above 24°C is likely to cause restlessness, and below 12°C makes it difficult to fall asleep. Your body needs to cool down to fall asleep. Your core temperature drops in the evening to trigger melatonin production, and a warmer room blocks that signal. Whereas, heat disrupts REM sleep, which is the stage most tied to memory, mood and emotional processing. That's why a hot night can leave you feeling groggy and irritable the next day.

• When sleeping, over 65’s generally need their rooms at a minimum of 18°C, versus 16 - 18°C for younger adults.

• When sleeping, aim for roughly 40 - 60% relative humidity. Anything above 60% and your sweat can't evaporate, so you feel hotter than a thermometer says.

• If you’re struggling to sleep due to high heat or humidity levels, you should cool down your bed, not just the room. Breathable mattresses, cooling pillows and lower-tog bedding do more for your comfort than the thermostat alone.

It's the argument every household has at least once a year. One of you is under the duvet with socks on - the other has a leg out with the window open and a fan pointed at their face. Somewhere between those two positions is a temperature you can both live with - and, as it turns out, there's a fair bit of science pointing to where that is.

Sleep temperature is one of those things almost nobody thinks about until it's a problem. But it's one of the biggest influences on how well you sleep; sitting right alongside light and noise as the three environmental factors that make or break your night's rest. So, what is the best temperature for sleep? That depends on a few things. Read on to find the perfect room temperature for you.

what is the optimal room temperature for sleeping?

For most adults, the ideal room temperature when sleeping that’s recommended by The Sleep Charity and the NHS is 16-18°C. This range is typically cooler than the temperature most people keep their living rooms. Many of us assume a comfortable bedroom should feel like a comfortable lounge at around 20-21°C, but your body’s sleeping needs differ from your relaxing needs. A room that feels slightly cool when you first get into bed is usually the sweet spot, because your bedding will do the rest. Here's an insight into each temperature setting and what they could mean for your sleep:

Below 12°C - Anything below this is considered too cold. You’ll experience difficulty falling asleep, your muscles will tense up, and you may have a restless night's sleep.

12-15°C - This temperature range is chilly and not recommended, but workable with warmer bedding, especially materials like fleece and brushed cotton.

16-18°C - This is the recommended range for most adults.

16-20°C - This is the recommended range for babies.

19-21°C - Whilst acceptable, this range is often too warm for hot sleepers.

Above 24°C - This range is considered too hot. You may experience restlessness, frequent waking and disrupted REM sleep.

why your body needs to cool down to sleep

To understand why 16-18°C works, it helps to know what your body is trying to do at bedtime.

your core temperature drops before you sleep

Your body temperature isn't constant across 24 hours as it follows a daily rhythm. Body temperature peaks in the late afternoon and early evening, then begins falling as bedtime approaches. That drop isn't a side effect of getting sleepy; it's part of what makes you sleepy.

As your core temperature falls, your body begins melatonin production - the hormone that tells your brain it's time to wind down. Your body sheds this heat mainly through your skin, from body parts such as your hands, feet and face. This only works if the surrounding air is cooler than you are. In a warm bedroom, there's nowhere for that heat to go, so melatonin is delayed, and you lie there wondering why you're exhausted but wide awake.

quick tip: a warm bath or shower an hour before bed can help your body temperature drop. Your skin brings blood to the surface in the warm environment of the water, and when you get out, you shed heat rapidly, which will speed up the temperature drop your body is looking for.

heat affects REM sleep the most

Not all sleep is equal, and heat doesn't disrupt all of it equally. During REM sleep (the stage most associated with dreaming, memory consolidation and emotional processing), your body essentially switches off its internal thermostat. You stop shivering or sweating, meaning you temporarily lose the ability to regulate your own temperature and become almost entirely dependent on the room around you. So, in a room that's too warm, your body will cut REM sleep short to protect you from overheating. You may not wake fully, but you'll surface into lighter sleep, lose REM time, and wake in the morning feeling foggy, flat and possibly short-tempered without knowing why. If you've ever had a "bad night" in a heatwave despite being in bed the usual number of hours, this could be why that happened.

how does room temperature affect sleep quality and duration?

Room temperature affects sleep in two distinct ways: how long it takes you to fall asleep (sleep onset), and how well you stay asleep once you're there (sleep continuity and architecture).

what happens when your bedroom is too hot

Above roughly 24°C, you may start to struggle with your sleep. The following may happen:

• sleep onset is delayed: your core temperature can't drop, so melatonin production is held back.

• you wake more often: micro-awakenings fragment your sleep even when you think you slept through.

• REM sleep is reduced: your body prioritises preventing overheating over dreaming.

• you sweat: which dampens bedding, causing it to feel clammy and cool in a way that causes disruption.

• restlessness increases: more position changes, more duvets on-and-off and more disturbance to anyone else sharing the bed.

Sleeping too hot isn’t limited to summer. Many modern homes are well-insulated with central heating, so you may experience hotter sleep in winter months, too.

what happens when your bedroom is too cold

Colder room temperatures can cause problems too, particularly below 12°C:

• falling asleep takes longer: cold triggers vasoconstriction and muscle tension, both of which keep you alert.

• cold extremities are an obstacle to sleep: falling asleep easily is much harder with cold feet, because your body sheds heat through them.

• draughts are worse than a steady colder temperature: an inconsistent draught across the bed causes more waking than a steady cool temperature throughout your room.

• stiffness on waking: as muscles tense against the cold, feeling stiff when you wake can be more common.

The fix for cold sleepers or cold rooms is usually easier solved than hot rooms or people who sleep hot: bedding layers, a higher-tog duvet, and warming your feet before bed are all great solutions to a cold room.

tips for maintaining an ideal bedroom temperature

• get a room thermometer: you cannot manage what you don't measure, and almost everyone guesses their bedroom temperature wrong. This is the cheapest fix on the list and the one that makes every other fix smarter.

• have a warm bath or shower an hour before bed: the post-bath temperature drop is one of the strongest natural sleep signals you can take advantage of.

• turn the heating down or off overnight: radiators running through the night are the most common cause of an over-warm bedroom and turning them down saves money at the same time.

• ventilate before bed, not just during the night: ten minutes of proper airflow in the evening clears built-up warmth and stale, humid air far more effectively than a slightly cracked window all night.

• cool your feet if you’re too hot: because you shed heat through your extremities, cooling your feet lowers your whole-body temperature quickly. Out from under the duvet is often enough. If you’re cold, keep your feet warm with a pair of socks or use an electric blanket before bed.

• keep the room dark during the day in summer: closed curtains and blinds on a sunny-facing room can keep several degrees of afternoon heat out, which dictates how warm your room will be later on at bedtime.

• avoid alcohol close to bedtime: alcohol raises skin temperature and disrupts thermoregulation, which is part of why alcohol-affected sleep feels so unrefreshing.

how to stay cool in hot climates

• Open windows at opposite ends of the home in the evening to create a cross-flow airflow.

• Keep curtains and blinds closed through the day in sun-facing rooms.

• Switch to a 14.5 tog duvet, or a coverless duvet for lighter, more breathable cover.

• Use cotton or linen bedding rather than synthetics or brushed cotton.

• Keep a glass of cold water by the bed and stay hydrated through the evening.

• Use a fan positioned to move air across the bed rather than blowing directly at your face all night.

how to stay warm in cold climates

• Layer bedding rather than raising the thermostat if possible.

• Add a throw or blanket over the duvet rather than switching to a much higher tog.

• Draught-proof your windows and doors - draughts disturb sleep more than steady cool air.

• Warm the bed, not the room, with a hot water bottle placed at the feet before you get in.

• Close the curtains at dusk to trap radiator heat in the room.

• Keep the room to 16-18°C and use a warmer blanket or 10.5 tog duvet, a hot room with thin bedding sleeps worse than a cool room with good bedding.

Getting your sleeping temperature right doesn't have to mean a full bedroom overhaul. Sometimes it's as simple as swapping a pillowcase, cracking the window at the right time, or finally replacing a mattress that's been trapping heat for years without you realising. Whether you're a hot sleeper, a cold sleeper, or somewhere in between - we've got something that'll help. If you found this article helpful, check out our blog on night sweats.

Cited sources:

https://thesleepcharity.org.uk/information-support/adults/sleep-environment/ https://oxfordhealth.nhs.uk/camhs/self-care/sleep/difficulties/bedroom/