TL;DR
- 16–19°C (low 60s °F) is the target range — measure yours before changing anything
- Most bedrooms are too warm, and most people have never checked
- Bedding and mattress surface matter as much as the thermostat, and are cheaper to change
- A warm bath 1–2 hours before bed helps; a hot shower right before bed does not
- Get the room right before you spend anything on supplements
The Short Answer
The best bedroom temperature for sleep is between about 16 and 19°C (low 60s °F), because that is the range in which your core temperature can drop and stay down — and the practical first step is simply to measure what your room actually is, since most people are several degrees too warm without knowing it. It is the cheapest sleep intervention available and it works the same night, which is more than most supplements can claim.
First: Measure
This sounds almost insultingly simple, and almost nobody has done it.
Put a thermometer in the room where you actually sleep — not the hallway — and read it at the time you go to bed and again when you wake. The number is often surprising. Bedrooms in flats, upper floors, and rooms with electronics routinely run 22–25°C, which is well outside the useful range.
A cheap digital thermometer costs very little and pays for itself the first night you change something based on it.
The Target Range
16–19°C is where the evidence keeps landing. Within that:
- Colder is not better. Below about 16°C you start waking from cold, and shivering raises core temperature — the opposite of what you want.
- Warmer is clearly worse. Above ~20°C sleep gets measurably shallower, especially in the second half of the night.
- Consistency matters. A room that swings several degrees overnight is harder to sleep in than one that holds steady.
If you cannot control the temperature precisely, aim to get into the range rather than to hit an exact number.
Bedding: The Cheaper Lever
If you cannot change the room — rented flat, no AC, shared thermostat — change the bed.
Layers beat a single heavy duvet. A heavy winter tog run year-round is one of the most common causes of overheating. Use a lighter base layer and add a blanket you can push off.
Material matters. Natural fibres breathe; synthetics trap heat and moisture against you. If you wake damp rather than hot, this is usually the reason.
Mattress surface. Memory foam is the classic offender — it is a temperature-holding material by design. If you sleep hot and you are on memory foam, a breathable topper is a cheaper test than a new mattress.
The Warm Bath Paradox
A warm bath or shower 1–2 hours before bed helps. Right before bed it hurts.
The mechanism is straightforward: warm water dilates the blood vessels near your skin, so when you get out you dump heat rapidly and core temperature falls. That takes time to set up — if you get straight into bed you have added heat without the payoff.
This is one of the few timing details that genuinely changes the outcome.
What Not To Bother With
- Electric blankets left on. They are for getting into a warm bed, not for staying warm all night.
- "Cooling" supplements. There is no capsule that meaningfully lowers core temperature. Glycine has a modest real effect — see Glycine for Sleep — but it is a top-up on a cool room, not a replacement.
- Fans without changing the bedding. Moving warm air over a warm duvet does not remove heat from you.
Where It Fits In The Bigger Picture
Temperature is one of the three levers in the Complete Guide to Perimenopause Sleep — alongside evening light and what you take before bed. Of the three, it is the one you can fix tonight for almost nothing.
If you are specifically waking hot, see Why You Wake Up Hot at 3am for the mechanism.
Frequently Asked Questions
Is 18°C too cold to sleep in? No — it is near the middle of the useful range. It feels cold getting in, which is why a warm bath beforehand and a layer you can remove work well together.
What if my partner likes it warmer? Compromise on the bedding rather than the room: a lighter duvet on your side, an extra blanket on theirs. It is much easier than fighting over the thermostat.
Do I need air conditioning? Usually not. Getting from 24°C to 20°C is most of the benefit, and that is often achievable with ventilation, a lighter duvet, and a fan pointing at you rather than at the room.
Does a hot room affect deep sleep specifically? Yes. Warmth suppresses slow-wave sleep more than it affects other stages, which is exactly why you can spend eight hours in bed and wake unrefreshed.
Should the room be dark as well as cool? Both matter and they work together. See the Evening Light Hygiene Stack for the light side.
Related
- The Complete Guide to Perimenopause Sleep — start here
- Why You Wake Up Hot at Night
- Glycine for Sleep
- The Evening Light Hygiene Stack
Get the free guide
The free perimenopause sleep guide covers the full order of operations — what to fix before you buy anything.
† These statements have not been evaluated by the Food and Drug Administration. This product is not intended to diagnose, treat, cure, or prevent any disease.