To cool your body off. If it is hot and you are sweating your body is providing water for cooling your body off. To maintain homeostasis you need to keep a balanced temperature right. to do that you need to sweat on a hot day.
Homeostasis is the tendency of an organism to regulate its internal conditions to maintain good health. Humans sweat, shiver, and can experience an increase in heart rate and breathing rate to maintain their internal temperature.
