A good night’s sleep does not solely depend on the quality of your mattress or your evening habits. The ambient temperature of your room also plays a crucial role in sleep regulation. Numerous studies show that our bodies need specific thermal conditions to fall asleep quickly and enjoy restorative sleep.

Temperature and Sleep: An Essential Biological Relationship

How Our Body Regulates Temperature During Sleep

The body follows a circadian rhythm, a 24-hour internal clock influenced by light and temperature. As bedtime approaches, the body temperature naturally begins to drop by 0.5 to 1 °C. This drop signals the brain that it is time to sleep by triggering the secretion of melatonin. A room that is too warm or poorly ventilated interferes with this mechanism, delaying sleep onset and fragmenting cycles.

A Myth to Debunk: “You Need to Heat the Room to Sleep Well”

For a long time, it was believed that sleeping in a warm room was comfortable. However, scientific data and recommendations from experts, such as the National Institute of Sleep and Vigilance (INSV), advocate for cooler temperatures for optimal sleep. A slightly cool room promotes deep sleep — the most physically restorative phase.

Ideal Room Temperature: Recommendations

  • Adults: between 16 and 18 °C is generally recommended.
  • Babies: slightly warmer, between 18 and 20 °C, for increased thermal safety.
  • Elderly: also 18 to 20 °C, due to increased sensitivity to cold.

These recommendations are validated by the INSV, Public Health France, and other European organizations.

Why a Cool Room Promotes Sleep

  • Facilitates the natural drop in body temperature necessary for falling asleep
  • Improves the quality of deep sleep, a physically and immunologically restorative phase
  • Reduces nighttime awakenings related to thermal discomfort
  • Limits nighttime sweating, a factor that degrades bedding

Consequences of Inappropriate Temperature

Room Too Hot

  • Difficulty falling asleep (the drop in body temperature is hindered)
  • Night sweats and micro-awakenings
  • Lighter and less restorative sleep
  • Increased risk of sleep apnea or snoring

Room Too Cold

  • Difficulty falling asleep if the cold exceeds 15 °C
  • Possible muscle tension, especially in the shoulders and neck
  • Frequent awakenings to warm up

Adapting to Climate

In Hot Areas

  • Use fans, silent air conditioners, or air coolers
  • Ventilate early in the morning or late in the evening, close shutters and blackout curtains during the day
  • Prefer lightweight bedding (cotton, linen, Tencel)
  • Choose high breathability bedding : pocket spring or latex mattresses, naturally ventilated

In Cold Areas

  • Regulated heating with a programmable thermostat
  • Duvets suitable for the season (heat index ≥ 400 g/m² for winter)
  • Thermoregulating mattresses or mattress toppers (latex, ventilated memory foam)

Find suitable breathable bedding → See the selection on lematelas.fr

Practical Tips for Optimal Temperature

  • Ventilate the room for at least 10 minutes morning and evening, even in winter
  • Avoid unnecessary heat sources (electronic devices on standby, excessive heating)
  • Install an indoor thermometer to monitor the actual room temperature
  • Adjust bedding to the season and your thermal sensitivity
  • If you have recurring issues with nighttime overheating, consider a high breathability mattress

The thermal environment is one of the most accessible levers to improve sleep. For an overview of factors related to room setup, check our guide on how the room influences sleep quality .

Mistakes to Avoid

  • Overheating the room in winter “for comfort”: the effect is opposite on sleep depth
  • Sleeping with windows closed in summer without any ventilation
  • Using the same duvet all year round without considering seasonal variations

FAQ: Room Temperature and Sleep

Why do we sleep better in a cool room?

The drop in body temperature is a biological signal that triggers the secretion of melatonin and facilitates entry into deep sleep. A cool room (16–18 °C) supports this process; a warm room hinders it.

Is a temperature of 21 °C too high?

For many profiles, yes. It is advised to aim for between 16 and 18 °C. Beyond 20 °C, several studies show an increase in micro-awakenings and a reduction in time spent in deep sleep.

What should I do if I don't have air conditioning in summer?

Ventilate heavily in the evening after 9 PM and early in the morning before 8 AM, then close everything during the day. A fan directed towards a window (not directly at you) improves air circulation. Sleep with just a lightweight cotton or linen sheet.

Is it dangerous to sleep in a room that is too cold?

Sleeping below 15 °C can disrupt sleep and cause muscle tension, especially in vulnerable or elderly individuals. An appropriate duvet largely compensates for a cool room.

Should I adjust the temperature according to age?

Yes. Babies (up to 3 years) and elderly people need a slightly warmer room (18–20 °C) due to less effective thermoregulation. For healthy adults, 16–18 °C remains the optimal range.