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Why Does the Sun Make you Tired? (FIND OUT HERE)

Why Does the Sun Make you Tired? (FIND OUT HERE)

The circadian rhythm links exposure to light to wakefulness and alertness. Yet, it seems ironic that spending some hours under the sun could make you tired. So, what is the correlation between sun exposure and tiredness, and what is the endpoint of the sleep-wake cycle?

Sun exposure leads to dehydration. It thickens your blood and prompts faster and harder blood pumping by the heart, leading to exhaustion. Other reasons include fatigue, sunburn, and thermoregulation.

Tiredness after sun exposure could be biological, medical, or consequential. We explored why the sun makes you want to lay down even though you slept well at night. In addition, we include tips for staying energetic and alert while out in the sun;


Exposure to sunlight and daytime heat prompts your body to sweat more. Sweating makes you lose more water and electrolytes quicker than usual, leading to dehydration. In return, you realize exhaustion since dehydration promotes blood thickness after losing blood volume.

The thickening of your blood hardens the blood pumping activity by your heart. Using more energy to pump blood to your brain reduces your energy levels, and you feel tired.

We recommend consuming a lot of water or healthy drinks like fresh juice before and during hours of sun exposure. However, avoid taking processed drinks like soda or caffeinated drinks like coffee.

In addition to staying hydrated, doctors also advise snacking on salty foods to replenish the lost sodium. These include salted crisps, sports drinks, and pickles. Sodium adjusts the blood fluid balance in the body, lowering the likelihood of dehydration.

awake sunlight

Your Body Is Struggling To Stay Cool

According to doctors, the sun's heat increases your body's internal temperature. However, the natural thermoregulation process involves your body constantly working towards maintaining an internal body temperature of 98.9 degrees Fahrenheit.

The hotter it gets, your body will use more energy to promote cooling during vasodilation. Here, blood pressure reduces when blood vessels expand and bring heat nearer to your skin for cooling. Such activity increases your metabolism to avail the energy required for thermoregulation. It promotes energy training, leaving you tired.

To avoid this, keep cool when under the sun. These include having a shade like an umbrella or hat and consuming cold and healthy drinks. Alternatively, we advise avoiding sun exposure during peak heat hours from 10 am to 4 pm. Limit your outdoor activities to early morning or late afternoon activities to allow for healthy thermoregulation.

We also recommend consuming cool healthy drinks to allow your body to cool off. Taking these cold liquids enables the heat to transfer to them. Your body eventually disposes of the heat via sweating or urine.


Exposure to the sun without a broad-spectrum sunscreen is the surest way of getting sunburnt and sun damage. However, sunburn is not only painful but also exhausting. The exhaustion resulting from sunburn happens when the sunburn increases your body temperature and uses extra energy to promote cooling.

We advise the daily religious use of sunscreen since doing so protects you from unprecedented sunburn and sun damage. Top this off by wearing breathable clothes that cover you in the sun. Carry an umbrella, a cap, and sunglasses, and reapply your sunscreen as necessary.

You Are Too Active

Most people look forward to Summer for many outdoor activities like hiking, running by the beach, speed boating, and swimming. However, indulging yourself in hyper-activity during the daytime could affect the human sleep-wake cycle.

Adenosine levels usually decrease during sleep and rise during the daytime. Such promotes wakefulness on sunny days. However, excessive physical activity under the sun triggers your body to release more Adenosine, leading to tiredness.

Alternatively, you could become tired from physical activity in hot temperatures. Strenuous physical activities like running, swimming, or exercising under the hot sun could lead to mental and physical fatigue. Besides, such exercises trigger your body to use energy and fluids, leading to dehydration and tiredness.

We advise timing your physical activity to hours with minimal sun exposure and heat. For instance, the sun is the strongest between 10 am and 3 pm. If you live in a hot and sunny location, limit your outdoor physical activity to morning hours or later in the afternoon.

You Have Activated Your Immune System

Study shows that constant exposure to Ultraviolet (UV) rays increases mental fatigue. It happens when exposure to UV light triggers your immune system to respond by trying to protect your skin. The increased activation of the immune system utilizes energy, resulting in one feeling worn out.

We advise using sun protection when out to avoid tiredness caused by an activated immune system during sun exposure. Such include wearing a broad-spectrum sunscreen with an SPF factor of 30+, covering your body, and utilizing shades.

Nature Wins

Being out for extended hours will naturally wear you out. It is because your body uses a lot of energy for high metabolism to keep you active and alert. Such explains why most people who have activities like hiking, running, swimming, or running want to sleep early.

When you are out in the sun, your body responds by suppressing the sleep hormone known as Melatonin. Contrarily, it triggers your body to release more Adenosine hormone. Such makes you stay alert and active during the daytime.

However, as it heads towards nighttime, your body starts producing more Melatonin and suppresses Adenosine production, making you feel tired and sleepy. Such is normal since most people are energetic when leaving the house in the morning but feel tired when evening approaches.

If this happens, we advise allowing your body to sync naturally to its sleep-wake cycle. Avoid caffeinated drinks like coffee or alcohol before bedtime, disrupting your circadian sleep cycle. Also, avoid exposure to blue light from screens like smartphones, televisions, or fluorescent tube lights.

You Are Straining Your Eyes

Some people are photosensitive, with the effect worsening with sunlight exposure. Exposing such people to excessive sunlight strains their eye muscles as they struggle to see through the seemingly blinding sunlight.

Also, the excessive sun promotes the intensity of reflections on reflective surfaces outdoors. Such straining could trigger headaches or migraines and make one feel tired and sleepy. By the time you are out of the sun, your mind and body are tired from all the mental and physical activities involved with eye-straining.

We recommend wearing glasses with a photochromic lens when out in the sun. Transition or photochromic lenses are adaptive to changes in the environment. For instance, they darken with sun exposure and lighten in the dark or under softer light. Besides, they have anti-glare, which dampens the glary outdoor lights, leading to less straining and better eye health.

sunlight bedroom

You Are Having An Afternoon Slump

Most people experience tiredness during the early afternoon, leading to a situation called an afternoon slump. Such happens in response to the circadian sleep cycle, where your body produces more Melatonin and less Adenosine towards the evening.

Besides, this, backed by strenuous physical activity under the sun, results in drowsiness during early afternoon hours. It is typical for most people to take a nap during this time.

We recommend indulging in activities that promote alertness to counter tiredness during an afternoon slump. These include playing a mentally-stimulating game, reading a book, or taking a walk.


The sun makes you tired in several ways, including dehydration, thermoregulation, sunburn, straining, or excessive outdoor physical activity. However, you can promote alertness during sunny days by staying hydrated, incorporating sun protection, and avoiding the peak sun hours.