How does the altitude affect the boiling point of water?

High-altitude cooking. is the opposite of pressure cooking in that the boiling point of water is lower at higher altitudes due to the decreased air pressure. This may require an increase in cooking times or temperature and alterations of recipe ingredients. read more

The boiling point of water, or any liquid, varies according to the surrounding atmospheric pressure. A liquid boils, or begins turning to vapor, when its internal vapor pressure equals the atmospheric pressure. read more

Because the atmospheric pressure is lower, the vapour pressure of the liquid needs to be lower to reach boiling point. Therefore, less heat is required to make the vapour pressure equal to the atmospheric pressure. The boiling point is lower at higher altitude. Here's a video that demonstrates the effect of atmospheric pressure on boiling point. read more