Here's Why Spending Time In The Sun Makes You So Tired

When you find yourself with nothing to do on a gorgeous sunny day, not a lot can stop you from basking in the warm glow outside. After all, relaxing in the sun takes no effort at all. But if it gets too hot, your body can have a strange reaction to the increase in temperature — it might make you feel super tired.

If you're living somewhere experiencing higher than average periods of heat, you may feel a lot more lethargic than you have during previous hot spells. For those living on the East Coast, you'll have recently experienced this feeling following the May heat wave (via silive.com).

There's more of that to come in the summer with temperatures potentially rising to "historic" levels never seen before, according to The Guardian. So as you prepare for the higher than average summer heat, here's how to better understand why higher temperatures can leave you feeling so exhausted.

As UW Medicine's digital publication Right as Rain notes, your body reacts to specific temperatures in different ways. Heat causes many chain reactions to cool your body down, including vasodilation and perspiration. Vasodilation is when the blood vessels widen so that heat can be brought closer to the skin by your blood (via BBC Bitesize) to help maintain your body's thermal regulation alongside sweating (via Mayo Clinic Proceedings).

Adding sweating into the mix can lead to dehydration as your body expels moisture to your skin to lower your core temperature. Unsurprisingly, both of these processes take up a lot of energy and can leave you feeling pretty fatigued. "A lot of tiredness stems from dehydration and vasodilation," family and sports medicine doctor Dr. Ashwin Rao told Right as Rain. "You lose some of your core fluid and blood circulating in your gut and brain because your body is instead trying to work on cooling you down."

In extreme heat, it's essential to note if you start feeling lethargic. Extreme fatigue can be a symptom of heat exhaustion, which, when left untreated, can turn into heat stroke — a condition that has the potential to be fatal (via Mayo Clinic). Though it may be challenging to differentiate between how you usually feel when you're tired and heat exhaustion, Dr. Ashwin Rao advises keeping an eye on how much you go to the bathroom. "If you realize you haven't peed all day, it's a sign that things are amiss," he told Right as Rain. An increased heart rate, a sudden stop in sweating, nausea, and confusion are also signs of heat exhaustion turning to heat stroke.

There are plenty of ways of preventing heat exhaustion and heat stroke from springing up on you, and it's all in the preparation. If you're planning to be out in the sun on a hot day, make sure you stay hydrated and avoid diuretics like alcohol and coffee. Always remember to wear sunscreen and keep in the shade as much as possible. You can still enjoy the summertime heat without being in direct sunlight — just make sure you keep an eye on the heat index (via the National Weather Service).