Heating are weaves in the One Power.
Heating a liquid[]
This is a very simple weave, formed by flows of element Fire. For example a very tiny thread of Fire is used by Aes Sedai to heat the water inside a teapot. A more powerful weave of this kind was used by Elayne to heat the water in a bath tube because it was becoming cold.
Heating the air[]
It is formed by flows of Air and Fire. It was used by Rand on the top of Dragonmount to warm the very cold air around him.