Body temperature must be controlled of human body else it starts destroying body cells. Human brain is a wonderful machine. Our brain has a system for controlling body temperature. 

This system keeps body temperature constant at approx. 37⁰C. When the body temperature starts to rise, then the brain stops burning of food to produce energy and opens the skin pores so that sweating can start. 

The evaporation of sweat causes the body to cool down.

During summers, temperature is hotter and the body overheats. When we get hot, our sweat glands are triggered and they release a watery substance in the form of sweat. 

When sweat is released onto the skin and is exposed to the air, it will evaporate and ultimately help to cool down the body and lower our body temperatures.