Sleeping in hot weather can be incredibly uncomfortable and disrupt much-needed rest. However, practical strategies exist for staying cool while sleeping and enjoying a refreshing sleep.
Thermoregulation is the process by which the body maintains a steady temperature.
Excessively high or low ambient temperature may affect sleep quality.
Sleeping in hot weather can lead to increased time spent awake and decreased time spent in slow-wave and REM sleep.
The ideal temperature for sleep is approximately 18.3°C or 65°F.
Strategies to stay cool while sleeping in hot weather include using a fan or air conditioning, drinking plenty of water, having good sleep hygiene, and keeping the bedroom’s curtains closed during the day.
Control of body temperature
The average temperature for a healthy individual is around 37°C or 98.6°F. Maintaining a steady body temperature is vital for proper bodily functions and survival. The process by which we achieve this is called thermoregulation.
The hypothalamus acts as the body’s thermostat, using the information it receives from temperature receptors located throughout the body. These receptors detect heat and cold can send signals to the hypothalamus, allowing it to monitor and adjust body temperature.
Our body uses various mechanisms to ensure that temperature stays within a narrow range. These mechanisms include releasing hormones, altering skin blood flow, sweating, and shivering.
Furthermore, the body naturally makes behavioral adjustments during sleep to adapt to the environment. For instance, if sleeping in a cold room, we might instinctively pull the covers up to keep ourselves warmer and more comfortable.
How temperature influences sleep
Our body temperature naturally fluctuates, adhering to a 24–hour cycle. During sleep, body temperature gradually decreases until it reaches its lowest point two to three hours before waking up in the morning. Then, it increases throughout the day and peaks a few hours before bed.
When we're awake, our body temperature is higher in the central parts of our body than in our hands and feet. As we become sleepier, our core body temperature drops.
When we sleep, the pineal gland in our brain releases a hormone called melatonin. This hormone causes the blood vessels in our fingers and toes to widen, allowing increased blood flow to those areas. As a result, the temperature in our extremities rises, helping to send heat away from the core.
Some people may feel hot in their upper body, but their feet remain chilly. Covering feet to keep them warm helps resolve this issue. This is because doing so helps to even out body temperature, which promotes better sleep.
Thermoregulation is active during sleep. So, excessively high or low ambient temperature may affect sleep quality. For instance, a study conducted in 2021 revealed that both high and low ambient nighttime temperatures were linked to an increased daily dose of sleeping medications among South Korean adults.
Sleeping in hot weather
Sleeping in extreme temperatures hot or cold can disturb sleep. With climate change, concerns about the potential increase in nighttime heat are increasing.
Studies suggest that exposure to cold temperatures has a more negative impact on sleep than heat. However, these studies were conducted with partially or fully unclothed participants, so the effects of clothing and blankets were not considered. When we can protect ourselves from the cold by using blankets and wearing appropriate clothing, the discomfort caused by heat becomes more upsetting.
Most people have dozed off in scorching heat and know the feeling of waking up feeling tired, drenched in sweat, and desperately thirsty. Some consequences of sleeping in hot weather include spending more time awake during the night and less time in deep sleep (known as slow wave sleep, or SWS) and REM sleep (crucial for memory consolidation). In humid conditions, moisture in the air prevents sweat from evaporating effectively. This leads to continuous dampness and hampers the efficient release of body heat.
Heat exposure has a stronger impact on sleep during the initial phases of sleep. Therefore, if air conditioning is limited, it can be a good idea to use it during this period.
The best temperature for sleep
According to the Sleep Foundation, the ideal temperature for sleep is approximately 18.3°C (65°F). This varies from person to person, but most people should sleep comfortably by setting the thermostat between 15.6–20°C (60–68°F).
However, infants are more sensitive to changes in ambient temperature as their bodies are still developing. Therefore, their bedrooms can be slightly warmer, around 20.5°C (69°F).
How to sleep while it is hot outside
Sleeping during the warmer months can be tough. With climate change, hot flashes will likely become more frequent, depending on the part of the world.
That's why learning effective ways to deal with them so they don’t disrupt sleep can be handy. Here are a few tips:
- Ventilation is key. A fan directed over bare skin helps promote sweating. Running a ceiling fan running overnight at low speed may also help. If there’s a cool period of the day, ventilate the room as much as possible before bed, then close the bedroom when temperatures rise.
- Be mindful when using air conditioning. Although an air conditioner helps cool a room, temperatures below 17°C can be detrimental to sleep. Additionally, excessive use of air conditioning consumes significant electricity, contributing to climate change.
- Stay hydrated. Drinking plenty of water during the day enhances temperature regulation during the night.
- Keep it cool. Close the bedroom’s curtains closed during the day. Keeping the sun out during the day will help keep the bedroom cooler at night.
- Dress for the occasion (or not). Choose comfortable pajamas made of natural fibers like cotton, bamboo, silk, or linen. These fabrics are breathable and wick away moisture, making them a good choice for hot sleepers. You may also sleep in your "birthday suit" if you prefer.
- Take a warm bath. Taking a warm bath an hour before bedtime helps promote a natural cool-down effect.
- Move the body. Exercise in the morning, when it's usually cooler outside — it helps promote better sleep at night and avoid daytime fatigue.
- Have healthy sleep habits. Help train the body to sleep better by having a consistent sleep schedule, a relaxing bedtime routine, and avoiding caffeine, large meals, and alcohol at night. Additionally, limiting exposure to bright light in the evening and getting some sunlight exposure during the day promotes better sleep.
With changing climate conditions, adapting and discovering methods to establish a cozy sleep setting is crucial while being mindful of energy consumption. Incorporating these strategies guarantees a peaceful and refreshing sleep, even on the hottest nights.
- Stat Pearls. Physiology, Temperature Regulation.
- Journal of Physiological Anthropology. Effects of thermal environment on sleep and circadian rhythm.
- Sleep. High and low ambient temperature at night and the prescription of hypnotics.
- Journal of Sleep Research. How to deal with sleep problems during heatwaves: practical recommendations from the European Insomnia Network.
- Sleep Foundation. Best Temperature for Sleep.