The temperature at which water vaporizes into steam is called a boiling point.
When the water reaches its boiling point, the hydrogen bonds between the water molecules start to break.
When the water reaches its heat of vaporization, water gets converted from the liquid state to the gaseous state.
Heat of vaporization
The heat of vaporization is defined as the energy which is required for transforming a given quantity of a substance from the liquid state to gaseous state under a given pressure.
The heat of vaporization of water is 540 cal/g at 100°C.