The science behind why you feel tired after being out in the sun all day

If you’ve ever spent any amount of time out in the sun, you’ve probably felt sun fatigue. This happens whenever you’re out at the pool, working in the yard, or even enjoying some time at the beach. If you’ve ever wondered exactly why your body gets so tired after being in the sun, there’s actually a very good scientific reason behind it.

See, when you go out into the sun, your body has to keep itself cool. One of the main ways that it does this is through the release of perspiration—or sweat—through the skin.