Why does water boil at a lower temperature at higher altitudes?
Water usually boils at 212F or 100C at sea level. As you go higher up in the atmosphere (higher altitude), the amount of atmosphere pushing down on you decreases, hence the pressure decreases. Water boils when the vapor pressure of the water equals the atmospheric pressure. Vapor pressure increases with increasing temperature, so when there is less atmospheric pressure, a smaller vapor pressure is required to get the water boiling, hence a lower boiling temperature.
