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Why Does Heat Make You Sleepy?

heat and sleep

If you’re out on a sweltering day, you are most likely to feel tired and sleep pretty soon. In fact, you don’t even have to be out in the sun to feel the effects of heat. A hot meeting room or a warm car ride can also make you feel sleepy and tried very easily. We all know heat makes us feel sleepy, but not many know why this happens.


Here are some possible reasons why we feel sleepy in the heat.


sleep dehydrationMore often than not, it isn’t the heat that’s making you feel sleepy, but rather the dehydration that happens as a result. When it’s hot and humid, the body quickly loses salt and fluid in the form of perspiration, which can lead to dehydration in a short time. Dehydration always causes sleepiness and fatigue. To keep yourself from getting dehydrated, drink sufficient water to provide your body with the hydration it needs. Although heat and fatigue don’t always mean dehydration, drinking plenty of water will keep your body’s water content replenished.


Cooling effect

cooling sleepThe body has its own mechanism of keeping cool. That’s why we sweat. Through the sweat glands, the body gives out heat in order to keep cool and regulate body temperature. The body expends energy in order to keep cool, and the more we sweat, the more energy we lose, leading to fatigue and sleepiness. The same thing happens when we are engaged in any strenuous physical activity like running or lifting weights. The purpose of sweating is to keep the body temperature consistent and prevent overheating. So the hotter the day and the more you sweat, the more tired you’ll feel because your body is using up your energy reserves.



comfort and sleepHeat isn’t always uncomfortable. There are times when heat is actually comforting. During winters, when everything is cold, being in a warm room can make you feel sleepy because it’s comforting. Other instances, such as taking a warm bath or having a hot drink, also emulate this same effect, because after your body temperature rises, it starts to drop. That’s when you feel sleepy. At the same time, overheating can also prevent you from a restful sleep. An overheated bed or mattress can prevent you from the sleep that you need.


Blood pressure

blood pressureWhen it’s warm, the blood pressure drops. When blood pressure is low, it causes fatigue and sleepiness. A slight drop in blood pressure means that there is less amount of blood reaching the brain, and as a result, your body struggles to stay awake. Although this is not a problem, if you get nausea and headaches it requires medical attention. A severe drop in blood pressure can be a sign of heat stroke.



sun and sleepWhen you’re out in the sun, your body stops melatonin production. When you get back in the shade, your body produces melatonin overtime. That’s the reason why you feel sleepy. Being in the sunlight makes vitamins like Vitamin D enter the body, and the sudden increase in metabolism drains the energy a little. The ultraviolet rays present in the sunlight also create chemical reactions in the body that cause fatigue and sleepiness. These chemicals reactions also cause skin damage sunburn, wrinkles, and even cancer.


By protecting yourself from sun exposure, it is possible to mitigate some of the sleepiness and fatigue. If possible, keep yourself away from the sun, at least from mid-day to late afternoons. If that isn’t possible, take some precautions when out in the sun. For instance, wearing long-sleeved clothing made from lightweight fabrics like cotton or linen helps the skin breathe and allows some of the heat to escape. Keeping yourself hydrated is also important, so drink sufficient water and eat some salty snacks to replenish the lost moisture. Even if you are out in the sun, stay in the shade if possible, or carry an umbrella or wear a hat. Sunglasses and sunscreen are two other essentials that you must not forget in summers. By minimizing the ultraviolet rays reaching you, it is possible to keep some of the sleepiness away.


Now that we know why heat makes us sleepy and how to stay safe, it’s time to enjoy summer while taking all the necessary precautions.

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