On hot days it maintains itself. by releasing heat and sweating
During summer, we perspire more because of the mechanism of our body which keeps us cool.During evaporation,the particles at the surface of the liquid gain energy from the surroundings or body surface and change into vapour.The heat energy equal to the latent heat of vapourisation is absorbed from from the body leaving the body cool.
Our body adjusts its body temperature on its own. In summers the outside temperature increases and the body temperature too increases therefore to reduce the heat in the body the cools itself by throwing out water from its body by perspiring.