When the temperature in your room is too hot or too cold, your body struggles to regulate its hormones, which can make falling asleep or staying asleep difficult. According to the Sleep Foundation, the ideal room temperature for sleep falls between 60°F (15.5°C) and 68°F (20°C). This range helps your body’s natural thermoregulatory process, which is essential for falling asleep quickly and getting good quality sleep.

Understanding the Body’s Temperature Regulation

The human body has an incredible ability to maintain a stable internal temperature, regardless of the external environment. It achieves this through various physiological responses like sweating, shivering, and changes in blood flow to the skin.

Sweating is the body’s primary method of cooling down. When your internal temperature rises, your sweat glands produce moisture that evaporates from the skin’s surface, releasing heat and cooling you down. On the flip side, shivering helps you warm up when your internal temperature drops. It’s an involuntary response where muscles contract rapidly, generating heat.

Blood flow adjustments also play a crucial role in temperature regulation. For example, when you need to cool down, blood vessels near the skin’s surface dilate, increasing blood flow and helping release heat. Conversely, when you need to conserve heat, these blood vessels constrict, reducing blood flow and helping you retain warmth.

These mechanisms are at work when you’re getting ready for bed and transitioning through different sleep stages. You’ve probably noticed this yourself—for instance, when your feet get cold in bed, putting on socks helps you feel warmer because a significant amount of heat is lost through your extremities. Similarly, if you’re too warm under the covers, sticking your feet out might be just the relief you need to fall asleep.

The Connection Between Temperature and Sleep

Throughout human evolution, temperature has been a key factor in signaling sleep and wake times. Temperature serves as a “zeitgeber” or time-giver, an external cue that influences our circadian rhythm. Studies of pre-industrial societies show that people typically fall asleep as the temperature starts to drop and wake up as the temperature begins to rise.

Temperature also impacts the different stages of sleep. About two hours before you fall asleep, your core body temperature starts to drop, reaching its lowest point during slow-wave sleep. Your brain temperature also decreases slightly at this time.

While your core body temperature typically hovers around 98.6°F (37°C), it fluctuates by about two degrees Fahrenheit during the night. This drop in temperature is due to reduced metabolic output, decreased muscle tone, and vasodilation, which leads to heat loss through your skin.

Melatonin, often associated with light exposure, is also influenced by room temperature. A cooler environment can enhance melatonin production, helping you sleep better. However, if your room is too warm, it can negatively impact both REM (Rapid Eye Movement) sleep, where dreams occur, and slow-wave sleep, which is essential for physical and cognitive recovery.

Research shows that even mild heat exposure during sleep can decrease REM sleep, increase wakefulness, and cause more sweating, leading to poor sleep quality. On the other hand, a room that’s too cold might force your body to expend energy to stay warm, preventing it from entering deep sleep stages.

The Benefits of Sleeping in a Cooler Room

While it may seem minor, room temperature can significantly impact your sleep. If you’ve ever struggled to sleep during a summer heatwave, you know how crucial it is to have a cool environment for restful sleep. Here are four reasons why you might want to turn down the thermostat tonight:

1. Better Sleep Quality: Sleeping in a cool room helps your body produce adequate melatonin and keeps cortisol (the stress hormone) levels low, which can prevent you from waking up in the middle of the night.

2. Fall Asleep Faster: A cooler environment helps your body lower its core temperature, making it easier to fall asleep. If you usually take 10–20 minutes to fall asleep, you’re in a healthy range. Insomniacs often have trouble sleeping because their core temperature remains high, keeping them awake.

3. Improved Weight Management: Cold temperatures activate brown fat, a metabolically active tissue that helps burn white fat, the type around your abdomen. Studies have shown that sleeping in a cool room can double the amount of brown fat in your body.

4. Lower Risk of Diseases: The increase in brown fat also boosts insulin sensitivity, which can help prevent type 2 diabetes and other metabolic disorders. Moreover, cool sleeping conditions might reduce the risk of Alzheimer’s disease by ensuring you get enough restorative sleep.

What If You Don’t Have a Thermostat?

Even if you don’t have access to heating or cooling systems, you can still create a cooler sleeping environment. Taking a warm bath or shower before bed might seem counterintuitive, but it can help lower your body temperature afterward, aiding sleep.

Researchers have found that water-based passive body heating, like a warm shower or bath, positively impacts sleep metrics, including how quickly you fall asleep and overall sleep quality.