Surely everyone has heard the helpful suggestion that you should drink a hot tea to cool down in summer rather than an ice-cold lemonade.
The reasoning is that the hot drink makes the body sweat and sweating should have a cooling effect. The problem with this logic lies in the laws of thermodynamics. During sweating, the evaporation of moist sweat creates a cooling effect on the skin. However, the amount of heat dissipated from the body in this way will never be greater than the amount of heat that enters the body through the hot drink.
The body also reacts to the additional heat by expanding the blood vessels near the surface of the skin. This gives you a feeling of inner warmth and a slightly heated face after drinking a hot drink.
Hot tea in hot temperatures stimulates sweating, which has a cooling effect on the skin, but the cooling effect is not sufficient to offset or even exceed the heat consumed. In addition, some of the fluid is lost through sweating and you have to drink more to quench your thirst.
