05.03.2026
Why Body Temperature Matters for Sleep
Body temperature usually peaks in the late afternoon or early evening, around 6 p.m., when alertness and physical performance are at their highest. Later in the evening, a gradual cooling process begins. This drop in core temperature is a key biological signal that prepares the body for sleep.
Once sleep begins, body temperature continues to fall and remains low throughout the night before rising again toward morning. Importantly, this rhythm persists even after poor sleep. That is why people often feel more alert during the day - even after a short or restless night - simply because their body temperature is rising.
How Aging Affects Temperature Rhythms
Circadian temperature rhythms change with age. In older adults, the daily rise and fall in body temperature tends to occur earlier in the day. As a result, many elderly individuals feel sleepy earlier in the evening and wake earlier in the morning. Research has also found that the amplitude of temperature rhythms often becomes smaller with age. This may partly explain why sleep in older adults is often lighter and more fragmented.
Body Temperature and Insomnia
Recent research on the physiology of insomnia suggests that temperature regulation may play an important role in sleep difficulties.
Several studies have shown that people with insomnia often display smaller fluctuations in their daily body temperature rhythm compared to good sleepers. Their bodies may have difficulty producing the natural nighttime drop in temperature that helps initiate sleep.
Sleep and temperature are also closely linked to melatonin, the hormone that regulates the sleep–wake cycle. Melatonin production increases in darkness and signals the body to cool down, preparing it for sleep. Exposure to light, especially natural daylight, suppresses melatonin and promotes wakefulness by encouraging body temperature to rise.
Unfortunately, modern lifestyles often disrupt this natural cycle. Studies have shown that many people receive less than one hour of direct sunlight exposure per day, while artificial lighting in the evening reduces exposure to true darkness. Both factors can weaken circadian rhythms and interfere with healthy temperature regulation.
One simple strategy for improving sleep onset—especially for people who struggle to fall asleep—is to increase exposure to early morning sunlight. This helps reset the circadian clock so that body temperature rises earlier in the day and falls earlier at night.
Strategies to Strengthen Your Temperature Rhythm
- Open curtains or blinds immediately after waking
- Eat breakfast near a sunlit window
- Avoid wearing dark sunglasses early in the morning
- Take a short walk outdoors soon after sunrise
- Spend time outside again in the late afternoon
- Sit near natural light during the hour before sunset
Regular exposure to natural daylight helps synchronize the body’s internal clock and reinforces the natural temperature cycle that promotes healthy sleep.
Why a Warm Bedroom Can Keep You Awake
Bedroom temperature plays a critical role in sleep quality. In order to fall asleep, the body must release heat and lower its core temperature. When the sleeping environment is too warm, this cooling process becomes more difficult.
As a result:
- Falling asleep may take longer
- Deep sleep may be reduced
- Nighttime awakenings may become more frequent
This is one reason why sleep quality often declines during hot summer months.
Cooler rooms, on the other hand, allow body temperature to drop more efficiently, helping the brain transition into sleep. Sleep experts typically recommend maintaining a bedroom temperature of around 18°C (65°F) for optimal sleep.
You can help maintain a cool environment by:
- Lowering the thermostat at night
- Opening a window for fresh air
- Using a fan or air conditioning
- Choosing breathable bedding materials
Your Mattress Can Influence Sleep Temperature
While many people focus on room temperature, the sleep surface itself can significantly affect thermal comfort.
Mattresses that trap heat can interfere with the body’s ability to cool down during sleep. Thick, dense memory foam layers, especially older designs often retain body heat and reduce airflow, causing sleepers to feel warm or restless during the night.
Modern sleep systems increasingly incorporate materials designed to improve temperature regulation. These may include:
- Breathable latex layers, which allow airflow through the mattress structure
- Lamella system which promote internal ventilation
- Ventilated foams, engineered with airflow channels
- Phase-change fabrics such as Outlast® technology
Outlast® materials were originally developed for NASA and are designed to absorb excess heat when the body warms and release it when the body cools, helping maintain a more stable sleep temperature throughout the night.
Similarly, pillows can affect thermal comfort. Some pillows act as heat traps, while others—such as those made from latex, ventilated foam, wool, or breathable fibers—allow better airflow and help regulate temperature.
Practical Ways to Stay Cool While Sleeping
Maintaining a cooler body temperature at night can make it easier to fall asleep and stay asleep.
Consider the following strategies:
Keep the bedroom cool
Set your thermostat to around 18°C (65°F). A slightly cooler environment supports the body’s natural cooling process during sleep.
Choose breathable sleepwear
Some people sleep comfortably in lightweight pajamas, while others prefer minimal clothing or sleeping without sleepwear. The key is to avoid heavy, insulating fabrics that trap heat.
Use temperature-regulating bedding
Lightweight duvets, breathable sheets, and mattress covers designed to dissipate heat can help prevent overheating.
Stay hydrated
Keeping a glass of cool water on your bedside table can provide relief if you wake feeling overheated during the night.
Use cooling aids when necessary
On particularly warm nights, a cool pack or chilled cloth can help lower skin temperature quickly.
In summary, sleep is closely tied to the body’s natural temperature rhythm. Supporting this rhythm—through daylight exposure, a cool bedroom environment, and temperature-regulating sleep products—can significantly improve sleep quality and reduce nighttime awakenings.
