Best Bedroom Temperature for Sleep: How Cool or Warm Should Your Room Be?

Written and Reviewed by the Cognitive Train Team
← Sleep

The best sleep temperature is not simply “as cold as possible.” Your room should help your body release heat while your bedding keeps your skin comfortably warm.

For many adults, a practical experiment is to begin in the upper teens Celsius—the mid-60s Fahrenheit—and adjust from there. That is a starting zone, not a biological law. Bedding, pajamas, humidity, airflow, age, health, climate, and personal preference can move the comfortable setting several degrees in either direction.

The research does not identify one perfect thermostat number for everyone. It does show a consistent pattern: excessive heat is disruptive, severe cold can also disturb sleep, and the temperature inside the bed matters almost as much as the temperature of the room.

Why Temperature Changes as You Fall Asleep

Sleep onset is tied to a drop in core body temperature. In the evening, blood vessels in the hands and feet widen, allowing heat to move from the body’s core toward the skin and then into the environment. The body is not becoming cold; it is redistributing heat in a way that supports the transition into sleep.

In a laboratory study of thermoregulation and sleep onset, the temperature difference between distal areas such as the hands and feet and more central skin regions predicted how quickly people fell asleep better than core temperature, melatonin, heart rate, or subjective sleepiness. Warmer extremities signaled that heat was leaving the core efficiently.

This creates the apparent paradox: the room can be cool while the skin under the covers stays warm. A cool environment provides somewhere for excess heat to go; a comfortable bed prevents the skin from becoming so cold that the body must defend its temperature.

How a cool room and warm bed support sleep Four stacked panels show a cool bedroom, comfortably warm skin under bedding, heat moving from the core toward the hands and feet, and a gradual decline in core body temperature that supports sleep onset. The sleep-temperature paradox 1. The room stays cool A practical starting experiment: Upper teens °C / mid-60s °F ↓ 2. The bed stays comfortable Bedding and sleepwear create a warmer microclimate around the skin ↓ 3. Heat moves outward Warm hands and feet release heat from the body’s core ↓ 4. Core temperature falls Sleep becomes easier to initiate and maintain The thermostat is only one part of the system.

Why a Hot Bedroom Disrupts Sleep

When the room and bedding are too warm, the body has difficulty releasing metabolic heat. Sweating and increased skin blood flow may not be enough, especially when humidity is high or heavy covers trap heat. Sleep becomes lighter and more fragmented.

A major review of thermal environment and sleep concluded that heat exposure increases wakefulness and can reduce both slow-wave sleep and REM sleep in real-life conditions involving clothing and bedding. Cold can also disturb sleep, but extra insulation often makes cold easier to correct than overheating.

Older adults may be particularly vulnerable to heat. In a controlled experiment, sleeping at 30°C rather than 27°C reduced total sleep time and sleep efficiency while increasing wakefulness in older participants. The findings are reported in a 2022 experimental study.

Can the Bedroom Be Too Cold?

Yes. Cold skin can trigger vasoconstriction, reduce heat loss from the core, and create discomfort or brief arousals. The answer is not to turn the bedroom into a refrigerator.

Bedding changes the threshold dramatically. The same thermal review found little difference in sleep across surprisingly wide room-temperature ranges when clothing and covers were available. A colder room may work well under a suitable duvet, while the identical thermostat setting can feel intolerable with thin bedding or exposed feet.

A sleepwear and bedding experiment found better sleep outcomes at 17°C than at 22°C under its tested conditions, but that does not make 17°C universally superior. Fabric, insulation, participants, and laboratory setup all shaped the result.

Why Older Adults May Sleep Better in a Warmer Room

The “keep it at 18°C” advice can be too rigid for older sleepers. Thermoregulation changes with age, and a setting that feels refreshing to one person may produce cold stress in another.

A year-long observational study of community-dwelling older adults found that sleep was most efficient and restful when nighttime bedroom temperature was between 20°C and 25°C. Sleep efficiency fell by a clinically meaningful 5–10% as temperature rose from 25°C to 30°C, but there was also substantial variation between individuals.

The useful lesson is not that everyone over 65 needs exactly 22°C. It is that age, circulation, bedding, and personal thermal comfort matter enough to make one universal number misleading.

A Better Way to Find Your Temperature

Start with a reasonable range and treat the thermostat as an experiment rather than a score:

  1. Begin in the upper teens Celsius (mid-60s Fahrenheit). Start slightly warmer if you tend to feel cold or use light bedding.
  2. Hold the setting for three nights. One night can be distorted by stress, exercise, alcohol, illness, or random awakenings.
  3. Change only one degree at a time. Large changes make it harder to identify what improved.
  4. Track comfort, awakenings, and morning alertness. The best setting is the one that reduces heat or cold discomfort without making the room feel hostile.

If you wake sweaty, throw off the covers repeatedly, or seek the cool side of the pillow all night, reduce insulation or temperature. If your feet stay cold, your muscles tense, or you curl tightly to conserve warmth, add socks or bedding before assuming the entire room must be warmer.

The free Sleep Calculator can help protect enough sleep opportunity while you adjust the environment. A better temperature cannot compensate for a sleep window that is simply too short.

Bedding, Humidity, and Airflow Change the Answer

The thermostat measures room air, not the climate under the covers. Mattress materials, duvet thickness, sleepwear, body position, and whether you share the bed all change heat retention. Two partners can therefore experience the same room as different thermal environments.

Humidity matters because it changes how efficiently sweat evaporates and how warm the air feels. A practical comfort target is often around 40–60% relative humidity, but climate, building conditions, and respiratory comfort may require adjustment. Airflow from a fan can make a warm room more tolerable without lowering the thermostat as much.

Separate duvets, breathable layers, or a fan aimed toward only one side of the bed can solve partner differences more precisely than forcing one person to tolerate the other’s preferred temperature.

Why a Warm Shower Can Help Before a Cool Night

A warm shower sounds like the opposite of cooling down, but timing changes the effect. Warming the skin widens peripheral blood vessels. After leaving the water, that circulation can help the body release heat more efficiently.

A 2019 systematic review and meta-analysis found that warm bathing or showering at 40–42.5°C, scheduled one to two hours before bed, was associated with faster sleep onset and improved sleep efficiency. The benefit came from supporting later heat loss, not from keeping the core hot in bed.

Temperature Is Not Always the Real Cause

Repeated night sweats, fever, hot flashes, breathing problems, medication effects, or sudden changes in temperature tolerance may disrupt sleep even when the room itself is reasonable. Persistent drenching sweats, unexplained fever, chest symptoms, or a major new sleep problem deserve medical attention rather than endless thermostat adjustments.

For ordinary experimentation, morning function provides useful feedback. The Alertness Test can track sustained attention, the Reaction Time Test can track simple response speed, and the Short Term Memory Test can provide a recall baseline across cooler and warmer nights. These comparisons cannot prove that room temperature caused the change.

The Next Part of the Sleep Environment

Once the room feels thermally comfortable, sound often becomes the next environmental question. A steady background noise can mask unpredictable disturbances, but it can also be unnecessary or irritating depending on the sleeper and the sound level.

What It All Comes Down To

The best bedroom temperature is cool enough to let the body release heat but warm enough—through bedding and sleepwear—to keep the skin comfortable. For many adults, the upper teens Celsius offer a sensible place to begin experimenting, not a target that must be obeyed. Older adults and people who run cold may sleep better several degrees warmer.

Use comfort, awakenings, and morning function to tune the setting rather than chasing one number from the internet. Continue with the white-noise guide, or explore the Sleep section for more on bedroom conditions, sleep timing, and nighttime disruption. Cognitive Train’s broader brain tests and collection of cognitive training tools can help you notice whether a better night carries into sharper attention and faster thinking the next day.