Why Does Heat Make You Sleepy? – 7 Reasons

Have you ever felt like taking a short nap after a day out in the sun?  Well, you are not the only one. Exposure to sun and heat has the same effect on everyone, and there are numerous scientific explanations for this. Let’s see why does heat make you sleepy?


When you are out in the heat, your body loses a lot of water and salt due to dehydration. Dehydration is known to increase the thickness of the blood, and this makes it harder for the heart to get blood to your brain.


This process can make you feel tired and sleepy. When we sweat, we also lose electrolytes which are essential for many body functions.

So, the next time you go out in the sun, ensure that you drink enough water to keep your body hydrated. Avoid drinking caffeine or alcohol-laden drinks as this can make the dehydration worse.

Temperature control

Our body works incessantly to maintain its inner temperature in the range of 98.6 degrees. So, when you spend time in the sun or if you expose yourself to heat, your body has to work extra to keep itself cool.

This heat exposure can increase our heart rate and our body’s metabolism. All this extra work done by the body can tire you out and this why you become lethargic and sleepy.

Chemical changes in the body

Spending excessive time in the hot sun exposes our skin to the damaging ultraviolet rays. Exposure to these UV rays causes biochemical changes that lead to sunburn, pigmentation and wrinkles. These chemical changes in the body can also make you tired and sleepy.

This happens because our body is working overtime to repair the damage caused by the sun. When you get sunburnt, the body diverts the fluids from the other parts of the body to heal the skin. This makes it much harder for you to sweat and cool down.

To avoid lethargy and skin damage, you must avoid direct exposure to the sun. Sit under an umbrella or in the shade whenever possible and wear a hat or a cap. Sip plenty of water through the day and have salty snacks. The ultraviolet radiation from the Sun is the strongest between 10 am to 3 pm. So, minimise outdoor activity during this time.

Power of nature’s light

When we are out in the sun, melatonin (sleep hormone) gets suppressed. However, as soon as the sun starts setting, our body starts producing this hormone. This effect is more pronounced when we spend the day out in the sun rather than when we are in the artificial lights indoors. So we tend to be sleepier after spending the day out in the sun and heat.

Psychological link

Over the years we have learnt to associate warmth with being cosy and sleepy. So when you feel warm, your brain links it to sleep and your body acts accordingly. This action is similar to how you link up certain songs or smell to something or some person from your past. You can use this psychological link of warmth with sleep by creating a warm atmosphere in your bedroom if you are suffering from sleep deprivation.

Low blood pressure

Our blood pressure drops when we spend too much time in the heat. This drop in blood pressure can make us lethargic, and also cause headaches and nausea. Drop in blood pressure means that there is less blood reaching your brain, which means there is a lesser amount of oxygen reaching your brain. This lack of oxygen can make you tired and sleepy.

Temperature drop in the body

When our body tries to cool down after spending some time in the heat, it tends to make us sleepy. This is similar to how we feel sleepy when our body cools down after a warm bath. So, while heat might make your tired, we start feeling drowsy when our body tries to cool down.



While heat does play a role in making you tired and sleepy, it does not necessarily guarantee a peaceful sleep. We can get better,  uninterrupted sleep if we sleep in a cool and comfortable room.


You May Also Like

Sleep Calculator – Know What’s the Best Time to Sleep

We all have different sleep needs depending on our age. Using an online sleep calculator is the easiest way to find the perfect sleep schedule. Having a specific sleep schedule can help you to get a restful sleep.

Voila Mattress Review – The “Best of Both Worlds” Hybrid Mattress

Available in three variants of firmness – Plush, Medium and Firm and built-in unique 12 layers, voila mattress is bound to be a favorite choice for mattress seekers.

Zenhaven Latex Mattress Review – The World’s Most Natural Sleep

If you want the natural feel of natural latex and do not prefer the spring or foam mattresses, then Zenhaven is just right for you. Zenhaven mattresses are made of Talalay latex, which is more resilient and has a supple and buoyant feel about it. It has two sides – firm and soft plush, any of which can be chosen by just flipping the mattress.

Cuddle Mattress Review – Sleep While Cuddling Your Partner Night Long

The Cuddle Mattress is designed for a unique purpose that is not available with any other mattress. You can dip your arms down the mattress and cuddle your partner comfortably during the night.

Tomorrow Sleep Mattress Review – Unique Hybrid Mattress Made Just For You

The Tomorrow Sleep mattress uses the best combination of memory foam and pocketed innerspring coils to make a unique hybrid mattress that has several advantages over others. It not only provides unmatched pressure relief, support and comfort but also maintains a cool temperature around the body.

More Articles Like This