Ideal Room Temperature for Sleeping: What It Is and How to Achieve It

The body needs to cool down in order to fall asleep. It is one of the conditions of sleep: internal temperature drops by about 1 ºC as bedtime approaches, and that signal helps trigger rest. A room that is too warm holds that process back. That is why you toss and turn on stifling nights.

The ideal bedroom temperature for sleeping is between 16 ºC and 19 ºC for most adults. It is not a magic number — it varies with the person, the pyjamas and the bedding — but it is the range in which the body works least to maintain the right temperature.

Why cool air helps you sleep

Sleep follows the rhythm of your internal temperature. At the end of the day it drops; in the morning it rises. A cool room reinforces that night-time drop and keeps you in the deep stages of sleep. A warm room does the opposite: the body spends energy trying to cool down, sleep becomes lighter and you wake up more often without knowing why.

Look at your hands and feet. When you start to feel sleepy, they warm up — that is the body releasing heat through the skin to lower core temperature. A cool room lets that mechanism work.

How to reach 16-19 ºC in summer

In the Portuguese heat, the challenge is bringing it down. A few simple measures:

• Close windows and blinds during the day to block the sun. Open them at night, when the air outside cools.
• Create a cross breeze between two windows or use a fan.
• Choose bedding made of natural fibres, which breathe better than synthetics.
• A lukewarm shower before bed helps: as you step out, the body cools down.

If you sleep badly in the heat every summer, I have gathered more strategies in the guide on how to sleep well in the heat.

And in winter?

The common mistake is heating too much. A room at 22-23 ºC with the heating on all night dries out the air and fragments sleep. Lower the thermostat to 16-18 ºC and compensate with a warmer duvet. It is more comfortable to sleep in a cool room with good bedding than in a warm, dry one.

Do not forget humidity

Temperature does not act alone. Ideal relative humidity is between 40% and 60%. Air that is too dry irritates the airways; air that is too humid feels stuffy and encourages dust mites and mould. In winter with the heating on, the air tends to dry out; on the coast in summer, it tends to rise. Airing the room for 10 minutes in the morning solves much of the problem.

The mattress counts too

The feeling of heat does not come from the air alone. Some materials retain heat more than others. Traditional memory foam, for example, tends to warm up; pocket spring mattresses let air circulate inside and dissipate heat better. If you wake up drenched even with a cool room, the problem may be underneath you. You can see the more breathable options in the spring mattresses collection, and if you have any doubts, we will call you and help you choose in 10 minutes.

A separate case: babies

Newborns regulate temperature less well and need a slightly warmer room, between 18 ºC and 20 ºC, without overheating. If you have doubts about your baby's sleep, always follow your paediatrician's guidance.

Temperature is one of the easiest pieces to correct and one of the most rewarding. Add it to darkness and silence and you have the essentials of a good bedroom. For the rest of the habits, the sleep hygiene guide brings everything together, and to set up the bedroom from scratch you can see how to create the right environment for sleeping.

— Ana Cristina, Sleep Advisor