Effect of atmospheric pressure on boiling points
The boiling point (the temperature at which a liquid boils) is influenced by the temperature at which the vapor pressure of the liquid equals the atmospheric pressure at sea level (760 mm Hg).
In reality, the atmospheric pressure changes daily with weather and elevation. Not even if one lives at sea level will there be a stable pressure of 760 mm Hg.
This affects both the boiling point of water (if you test run it, a thermometer shows 100C in boiling water) and the boiling point of alcohol, for us the azeotrope of 95% alcohol and 5% water.
We can use this phenomena to do vacuum distillation as well. When pressure lowers, the boiling point decreases, and when pressure is higher, the boiling point increases. Atmospheric pressure is measured with a barometer.
For conversions, you can use this boiling point calculator.