Brainstorm Answer: Relative Humidity Listen in RealAudio Email Your Comments

Dave Thurlow, Host

 
Is it possible to have a 95 percent relative humidity in the winter?

That's the most recent Weather Notebook Brainstorm question. Hi, I'm Dave Thurlow for the Mount Washington Observatory.

YES, it is possible to have 95 percent relative humidity in the winter. In fact, it's possible to have 96, 98, 99 or 100 percent as well. Why? Relative humidity is just a ratio between the amount of water vapor in the air and the highest amount of water vapor possible at the current air temperature. Be it 115 degrees, 15 degrees or 15 below. There always can be 100 percent relative humidity and any percentage below. But don't take my word for it. Listen to the reason and the rhyme from Jim Williman, Weather Notebook listener from Canton, NY, home of WSLU.

Air can hold water Sometimes quite a lot Less if it's cold And more if it's hot The amount of the water I think we can tell By reading humidity That rings a bell So when the air's soggy No more can it hold The humidity's high Be it ever so cold And when the air's dry So, it parches your skin The humidity's low And so we begin To unravel the mystery When it's 15 below That's Celsius Dave Just so that you know And the air's just as wet As can possibly be Then humidity 95 Is what we should see In absolute terms There's not too much there That's water I mean Dissolved in the air Which is why We do not feel sticky and wet On crisp winter mornings That's all that you get."

Absolutely. Even though relative humidity can reach 100 percent on a cold winter morning, it doesn't feel humid because in the winter 100 percent doesn't mean very much water in the air. Our show is produced and recorded by Bryan Sejvar and Sean Doucette the Weather Discovery Center in North Conway, New Hampshire.