Mountain top boiling
If you were on a mountain top you would find the water in a kettle would start boiling at less than 100 °C.
Why? Because the air pressure is much lower the higher up you are – and the lower the pressure the lower the temperature at which liquids boil.
You can change the temperature at which any liquid boils by changing the pressure. Boiling at a particular pressure is known as Vaporization or Evaporation.