Most of the shadows in this life are caused by standing in one's own sunshine. ~Ralph Waldo Emerson
Question #4941 posted on 04/12/2004 12:02 a.m.

Dear 100 Hour Board,
How do they determine humidity and how can you have over 100%?
- (Brad)

A: Dear (Brad),

Percent humidity is determined by taking the amount of water vapor in the air and dividing it by the amount of water vapor the air is capable of holding, then multiplying that number by 100. Because the amount of water vapor air can hold varies by temperature, Arizona can have more water in the air at 10% humidity than Washington does at 80% humidity.

You get over 100% when there is more water than the air can hold. That is, when water condenses out of the air and forms either rain or fog.

--Der Berliner