The circadian rhythm serves an important purpose in preparing the body for changes in the environment, such as anticipating times for physical activity, sleep and meals. The strongest external queue is the light/dark cycle, however, other external factors such as temperature can have significant effects on our internal body clock.

Heat has a significant impact on the circadian rhythm of living organisms. Heat affects circadian rhythm by regulating the release of the hormone melatonin, which is responsible for regulating the sleep-wake cycle. Humans have a sleep-wake rhythm that is repeated in a 24-hour cycle. Research has shown that exposure to high temperatures can disrupt the normal functioning of the biological clock and can suppress melatonin release, leading to changes in sleep patterns.

During sleep, the core body temperature drops, signalling to the body that it is time to sleep. Exposure to heat can raise the core body temperature and make it harder to fall/stay asleep. Heat can disturb sleep more than cold, especially in young and elderly people. This is because heat makes people more awake and decreases the time they spend in deep sleep. One reason for this could be that, if sleep is disturbed at the beginning, the body tries to catch up later on. Heat-related sleep problems don’t go away, even after several days of being exposed to heat: Even if people are sleep-deprived, heat still affects the amount of time in deep sleep. Wakefulness is the only stage that can help the body deal with high temperatures and it replaces deep sleep and dreaming to help the body stay at a normal temperature.

Therefore, it is important to keep the temperature in mind when it comes to sleep and wakefulness. For sleeping, the ideal temperature is about 18 degrees Celsius, which helps the body get into the best state for sleeping. It can lower the body’s temperature and make for a deeper, more restful sleep. If it’s too hot or too cold, it can interfere with sleep quality and make it harder to fall or stay asleep.