It sounds pretty counterintuitive, drinking hot liquids on a scorching hot day. But, hot beverages (tea included) can help cool our bodies down in hot weather. This practice has been seen for generations all over the world. In China, India, and beyond, people drink hot tea in sweltering climates. It is said that the hot liquid on our tongues triggers our internal cooling systems to start to cool the body down. We do this through sweating and other bodily mechanisms.
According to a study done by the University of Ottawa's School of Human Kinetics, our body heat storage lowers when we ingest warm liquids. This is due to the disproportionate modulations in sweat output from warm-sensitive thermo-sensors in our tongue, throat, and stomachs. The caveat is that our bodies need to be able to evaporate the increased amount of sweat produced. So in humid, or wet climates, it is much less likely we can do so.