A cooler room temperature generally makes a person feel sleepier and supports higher quality rest. The body’s ability to regulate its internal temperature, known as thermoregulation, is closely tied to the sleep-wake cycle. A slightly lower ambient temperature works in harmony with the body’s natural processes to initiate sleep. However, this beneficial effect is dependent on maintaining the temperature within a specific, comfortable range.
How Temperature Affects Sleep Onset
The transition from wakefulness to sleep requires a specific biological signal involving a drop in core body temperature. As part of the body’s circadian rhythm, this internal temperature begins to decrease naturally in the hours leading up to bedtime. This drop, typically between 1 and 2 degrees Fahrenheit, acts as a trigger for sleep initiation.
A cool external environment facilitates this necessary decrease by helping the body shed heat more efficiently. To offload heat, blood vessels near the skin’s surface, particularly in the hands and feet, dilate in a process called vasodilation. This draws warm blood away from the core to the extremities, where the heat is released into the environment. A cool bedroom supports this heat dissipation, accelerating the temperature drop needed to enter the Non-Rapid Eye Movement (NREM) stage of sleep.
The Optimal Sleep Temperature Range
To maximize the benefits of a cool environment, sleep experts recommend a room temperature between 60 and 67 degrees Fahrenheit (15 to 19 degrees Celsius). This range is considered optimal because it aids the body’s natural thermoregulation without forcing it to work too hard. A temperature within this window allows the body to maintain its lowered core temperature throughout the night without expending metabolic energy.
Staying within this specific range ensures the body does not have to actively generate heat to stay warm. This passive state of cooling supports the most restorative phases of sleep, particularly deep sleep. Setting the thermostat within this band provides the ideal conditions for sustained, high-quality rest.
When Excessive Cold Hinders Sleep
While cool temperatures are conducive to sleep, an environment that is too cold can become disruptive and counterproductive. When the ambient temperature drops significantly below the optimal range, the body shifts its focus from passive cooling to active heat conservation. This is a survival mechanism that overrides the signals for sleep.
In excessively cold conditions, the body initiates peripheral vasoconstriction, causing blood vessels in the extremities to constrict. This action retains warm blood near the core organs, actively preventing the heat loss necessary for sleep onset. If the cold persists, the body may trigger shivering, which is a form of thermogenesis that elevates the metabolic rate and increases core temperature. This metabolic activity and the resulting physical movement can cause micro-awakenings and prevent the consolidation of deep NREM and REM sleep.