I’ve always loved a cold bedroom. Window open, no heating, nose like an ice cube, that was very much my winter sleep aesthetic.

But then there are those nights when it drops to -3 degrees C outside, and you wake up at 3am feeling more like a mountaineer in a sleeping bag than a person peacefully “prioritising sleep hygiene”.

This had me wondering: is it actually good for us to sleep in such a cold room, especially with the window open, or is that just something we tell ourselves while we shiver under the duvet?

Let’s look at what the science says, and how to find a balance between fresh air, comfort and genuinely restorative sleep.

What Temperature Is Actually Best for Sleep?

Sleep researchers more or less agree on this:

Most adults sleep best in a bedroom somewhere around 15–19°C.

At night, your body naturally drops its core temperature by about 1°C to prepare for sleep. A cool bedroom helps this process along, which is why 

• You fall asleep more easily
• You get more deep and REM sleep
• You’re less likely to wake up feeling hot and restless at 3am

So yes, a cool room is genuinely good for sleep but there is a big difference between “cool” and “freezing”.

When Cool Becomes Too Cold

When your bedroom starts getting down towards 10°C and below, especially if the window is wide open, your body is no longer thinking,

“How wonderful, perfect sleep conditions…”

It’s thinking,

“Right, we’re camping now. Stay alive and stay warm.”

At very low temperatures:

• Your body has to work harder to maintain its core temperature
• Muscles tense up to prevent heat loss (hello, stiff neck and shoulders)
• You’re more likely to wake up in the night or sleep more lightly
• Stress hormones such as adrenaline and cortisol can creep up as your system stays on “cold alert”
• You might still fall asleep in a very cold room – especially if you’re tired – but the quality of your sleep is unlikely to be as good as it could be.

The Romance (and Reality) of Sleeping With the Window Open

There’s something wonderfully romantic about sleeping with the window open,  especially if you live in the countryside: night sounds, fresh air, owls, rain on the tiles.

And there are benefits:

• Lower CO₂ levels in the bedroom
• Less stuffy, stale air
• Many people say they feel clearer and more refreshed in the morning

However, when it’s very cold outside (around 6°C or less), there are some downsides:

• Cold air falling directly onto your face and chest can make you toss and turn
• Breathing very cold, dry air may irritate sensitive airways
• Your bedding has to work overtime to keep the rest of you warm.

So while a cracked-open window in spring or autumn can be wonderful, the “all the way open in near-freezing temperatures” approach is often more punishing than beneficial, especially over months of winter.

So… Should You Close the Window in Winter?

If the temperature is dropping towards that 6°C mark or below, then yes, in most cases, it’s kinder to your body (and your sleep) to close the window or just leave it very slightly ajar.

You’re not giving up on fresh air. You’re simply choosing:

• A cool, stable temperature over an extreme one
• Deeper, more restorative sleep over the “I’m hardcore” shivery feeling.                             
• You can still:

• Open the window wide before bed to air the room
• Leave the door slightly open for airflow
• Use breathable, natural bedding so the room feels fresh even with the window closed. 

How to Create the Perfect Winter Sleep Nest. 

Here are some simple tweaks that make a big difference when it’s cold outside:

1. Aim for “cool and cosy”, not “Arctic”

If you can, keep the bedroom somewhere around 15–18°C in winter:

• It still feels fresh and cool
• Your body doesn’t have to fight to stay warm all night
• You wake up feeling restored rather than tense and hunched

Even a very low-level background heat for a couple of hours in the evening can take the edge off icy rooms.

2. Layer Smartly: Why Lightweight Layers Work Better

Rather than one huge, heavy duvet, layers work beautifully:

• A breathable cotton Sleep Dohar
• A lightweight cotton quilt
• A wool duvet that you can add or remove in the night

This creates little pockets of warm air between the layers, so you’re snug but not suffocating. If you’re a “foot out of the bed” person, it also gives you more control, you can slide a layer back or poke out a toe without exposing your whole body to the cold.

Our Shades of Cool London Sleep  Dohars are actually perfect with this in mind: light, breathable cotton that lets your body regulate its own temperature, with just enough warmth to stop you from waking up chilled.

3. Keep the Draught Off Your Body

If you adore sleeping with the window open or at least cracked, try to:

• Move your bed so you’re not in the direct path of cold air
• Keep your head away from the window edge
• Use a slightly higher sheet or blanket over your shoulders and upper back

Cold on the face can be refreshing; cold on the kidneys at 3am is another story entirely.

4. Fresh Air Without Freezing

If you’re worried about a “stuffy” room with the window closed:

• Open the window wide for 10–15 minutes before bed while you’re brushing your teeth
• Do the same in the morning while you make your coffee
• Keep bedding natural (cotton, linen, wool) so it breathes

You’ll still have that lovely aired-out feeling, just without the midnight shivering.

Cold Isn’t the Enemy – Chronic Chill Is

Short bursts of cold can be invigorating, a winter walk, a cold dip, cool sheets when you first climb in.

But night after night of being genuinely cold in bed is more likely to:

• Disturb your sleep
• Tighten your muscles
• Leave you feeling less restored in the morning 
• The real sweet spot is a cool, comfortable room, breathable layers, and just enough fresh air – not a bedroom that feels like the inside of a fridge.

Bringing It Back to Real Life

If, like me, you love:

• No heating on in the bedroom
• Lots of fresh air
• That delicious feeling of getting into a cool bed

…you don’t have to give any of that up.

You might just experiment with:

• Closing the window on the coldest nights (or leaving it only slightly open)
• Adding one thin layer on the bed for example a Dohar 
• Aiming for cool and relaxed, rather than “I can see my breath” levels of cold

Your body – and your sleep – will quietly thank you 

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