Dear Tom,
If hurricanes feed off of water that is evaporated and if that occurs when the air
pressure is quite low, does this mean the boiling point of water varies depending on the
air pressure?
Carl Rollberg, Calumet Park, Ill.
Dear Carl,
Changes in air pressure do, indeed, affect the temperature at which water boils. The
boiling temperature falls as air pressure decreases (and as elevation increases).
Water, even cold water, evaporates at all temperature and air pressure values, and air
pressure is not a factor in providing moisture in hurricanes. Air pressure is not low
during the formative stage of a hurricane, and water vapor, from the evaporation of sea
water, is fueling the developing storm even then.
At sea level, water boils at 212 degrees; at 620 feet (Chicago's elevation), it boils at 211
degrees; but 1,450 feet up (the top of Sears Tower), at 208 degrees; in Denver, 202
degrees.
