Bedroom temperature and sleep: a useful range and how to adapt it

Core body temperature naturally drops around the time you fall asleep. To release that heat, the skin exchanges warmth with the surrounding air. In a warm bedroom, that exchange becomes harder, especially if the comforter traps heat or the air barely circulates.

A 2012 review summarizes laboratory studies: both heat and cold increase wakefulness, but in real life, under a comforter and in pajamas, it's mainly heat that reduces deep sleep and REM sleep. Humidity worsens this effect. Cold is partly offset by bedding. A 2024 systematic review confirms that, worldwide, higher outdoor or indoor temperatures are associated with shorter, lower-quality sleep, with a stronger effect on the hottest nights and in vulnerable people.

A 2023 study followed older adults at home using sensors in the bedroom and a sleep-measuring device. Sleep was most efficient and restful when the bedroom was between 20 and 25°C. Between 25 and 30°C, sleep efficiency dropped by 5 to 10%. Differences between participants were substantial.

This result doesn't contradict the often-cited 18-to-20°C benchmark. It concerns seniors, in their actual homes, who are often more sensitive to cold. The temperature measured in the middle of the room also doesn't describe the microclimate under the comforter. Neither 18°C nor 25°C is a requirement.

If you're too warm. First lighten the comforter or pajamas. Close shutters and curtains against the sun during the day, then air out the room as it cools outside, if noise and safety allow. A fan aimed at the bed can help. For ventilation, see also bedroom ventilation.

If you're too cold. Add a localized layer, a blanket, or socks rather than turning up the heat sharply, at the risk of waking up in a sweat.

For two people sharing a bed. Two comforters of different weights often resolve a mismatch better than a thermostat.

A warm shower before bed can also help lower body temperature, and a dark bedroom rounds out the environment.

1. 01Start from a comfortable setting, often 18 to 20°C.
2. 02Keep it for two or three comparable nights.
3. 03Note awakenings due to heat or cold, the bedding used, and how you feel in the morning.
4. 04Change one element at a time: comforter, pajamas, ventilation, or thermostat.
5. 05Go back if comfort gets worse.

Fragmented sleep can come from noise, light, caffeine, pain, or a sleep disorder. A well-adjusted bedroom doesn't treat persistent insomnia.