What is the best bedroom temperature for sleep?

What does research say about bedroom temperature?

Temperature is one part of the sleep environment. A review by Okamoto-Mizuno and Mizuno describes how heat, cold, humidity, clothing and bed covers influence sleep and temperature regulation. A room reading alone cannot capture the conditions around your body under the covers. [2]

In a laboratory study, 17 healthy young adults slept under combinations of sleepwear, bedding and room temperatures of 17°C and 22°C. Researchers measured sleep using polysomnography. Some outcomes depended on both sleepwear and temperature; they found no overall bedding effect in that experiment. This small study helps explain why a thermostat setting is only part of the picture. It does not establish the best temperature for every age group or climate. [3]

Does colder always mean better sleep?

No. Research on thermal conditions includes disruption from both heat and cold, with effects shaped by clothing and bedding. Lowering the thermostat further is not automatically helpful. If you keep waking to add blankets or feel uncomfortably cold, change the setup rather than forcing yourself to stay within a suggested range. [2]

The 18–20°C starting range comes from public-health advice. It is not a precise threshold derived from the small experiment above, and it should not become a reason to worry if you sleep comfortably at a different setting.

Why you can feel hot in a cool bedroom

The air temperature on the wall and the warmth inside your bed are different things. A heavy quilt, sleepwear, mattress protector and topper all contribute to your bed setup. Changing the room temperature while keeping every layer the same can miss the source of discomfort.

Try noticing where the warmth is concentrated. Does the whole room feel stuffy before you get into bed? Or do you feel comfortable until you pull up the duvet? These observations are practical clues, not a medical test. They help you choose a reasonable first adjustment.

Humidity also matters: research describes greater sleep disruption under humid heat in some experimental conditions. This helps explain why the same room temperature can feel different on different nights. [2] If you use a thermometer or humidity monitor, use it to notice patterns rather than checking it repeatedly through the night.

How to find a comfortable sleeping temperature

The following is a practical home-comfort experiment, not a clinical treatment protocol. Make one manageable change at a time so you can tell what helped.

1. Record the starting conditions

Before bed, note the room temperature if you have a thermometer, the cover you are using and whether the room feels warm, cool or comfortable. In the morning, record whether you woke feeling hot or cold. A short note is enough; there is no need to score every minute of sleep.

2. Adjust one layer or one setting

If the bed feels too warm, try a lighter cover first. If the entire room feels warm, consider a modest thermostat adjustment where cooling is available. Keep the other conditions similar for a few nights. Avoid interpreting one unusually good night as proof that a purchase or setting caused the improvement.

3. Check conditions later in the night

A timer may switch off cooling, outdoor conditions may change, or you may pull on a heavier blanket while asleep. If you wake uncomfortable, make a simple note the next morning. You can then adjust the timing or layers without repeatedly interrupting sleep to investigate.

4. Plan for different preferences

Partners can try separate lightweight covers before changing the whole room. If one person feels cold and the other feels hot, a shared thermostat may never solve both preferences. Use bedding choices that each person can adjust independently.

5. Work within your climate and budget

In a hot climate, reaching 18°C may be expensive or impractical. Focus on achievable comfort improvements and follow local heat-health advice during extreme weather. Our guide to sleeping cooler without AC introduces room and bedding options. A target temperature should never delay moving to a safer, cooler place when indoor heat becomes dangerous.

Which products might address the actual problem?

Choose a category after identifying what feels uncomfortable. These are selection criteria; this article does not claim to have tested or ranked specific products.

• Room thermometer: useful when you want to compare evenings or check whether the thermostat reflects the bedroom. Position it according to its instructions, away from direct sun or an air outlet.
• Lighter sheets or covers: worth considering when your existing layers feel excessive. Compare care requirements, texture and return terms in our cooling sheets guide.
• Fan: may suit a need for air movement. Check low-speed noise, stability and controls; see the bedroom fan guide. A fan does not lower the room's air temperature like an air conditioner.
• Mattress accessory: consider it when discomfort seems concentrated at the sleep surface. Check whether a cooling topper changes the support or feel you already like.

Cooling claims deserve perspective. A 2025 systematic review of nine trials found no clear pooled differences in standard sleep outcomes from the bedding interventions studied; evidence certainty was low or very low. Some studies suggested body-cooling effects. This does not mean every product is ineffective, but it does mean that feeling cooler and demonstrably improving sleep are different claims. [4]

When waking hot needs more than a room adjustment

Sweating because the room or bedding is warm is different from repeatedly soaking clothes and sheets despite a cool environment. NHS guidance recommends seeing a clinician for regular night sweats that wake or worry you, particularly with unexplained weight loss, a high temperature, cough or diarrhoea. [5]

Do not keep buying cooling products to explain persistent symptoms. The waking hot at night guide can help you organise observations, while a clinician can assess possible causes. This article addresses adult bedroom comfort; it is not guidance for infant sleep or a treatment for insomnia.

Bedroom temperature questions

Is 20°C too warm for sleep?

20°C equals 68°F, the upper end of the CDC/NIOSH starting range cited here. It is not automatically too warm. Consider your covers and how you actually feel overnight before adjusting it. [1]

Is 17°C better than 22°C?

The small laboratory study compared those settings and found differences in some sleep measures. Its young participants and controlled conditions cannot establish a universal winner. Use the finding as context rather than a prescription. [3]

Should I leave the air conditioner on all night?

There is no single schedule that fits every room. Consider whether the room becomes uncomfortable when it switches off, along with noise, energy cost and manufacturer instructions. If using a timer, change one setting and check your comfort over several nights.

Can a cooling sheet replace air conditioning?

A sheet changes the bed's feel; it does not control the room's temperature. If the whole space is dangerously hot, bedding is not a substitute for effective cooling or access to a cooler place.

What if I sleep well above the suggested range?

You do not need to chase a lower number solely because it appears in an article. If you are comfortable and sleeping well, consider the recommendation a reference point. Reassess when conditions or symptoms change.