Why does the sun make you sleepy?

Answer 1

Your body is using up energy to try to keep your body at a certain temperature.This is the same reason you become tired while taking a hot bath.

Answer 2

Exposure to sunlight triggers the release of the hormone melatonin, which helps regulate our sleep-wake cycle. Sunlight can also increase serotonin levels in the brain, which can contribute to feelings of relaxation and drowsiness. Additionally, spending time in sunlight can raise body temperature, and a drop in body temperature can make us feel sleepy.