Udisha
The sweat response
While it might come as a surprise, hot tea is actually the beverage you need in summers. Drinking tea tells your brain that your body is hot and that triggers sweat. Once it dries up, a significant amount of body heat is lost, making your body cooler. Drinking ice water has the opposite effect.
The effect on blood vessels
Ice water can tighten your blood vessels, trapping heat inside your core. Hot tea widens the blood vessels which makes it easier for the heat to move towards your skin surface and eventually release.
Lowering the core temperature
Temporary cooling doesn't help. Ice water can give you a brief relief, but it does not bring down your body temperature. While sweat might feel uncomfortable, it is most effective cooling system of the body, which is triggered by a hot beverage. Hot tea or coffee, therefore, does the job of lowering your body heat.
Humidity
Hot tea does not work in every environment. If the humidity is low and the weather relatively dry, the sweat can evaporate quickly, making you feel cooler, faster. However, in extreme humid conditions, a cup of hot tea might not do the trick and a cold beverage may be the more comfortable option.