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Brian Gotter: Welcome Back, Gotter

Dew Point vs Humidity

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After a weekend when Hurricane Irene pounded the East Coast, today is the 6th anniversary of the catastrophic Hurricane Katrina that hit Alabama, Mississippi and Louisiana.  We will never forget those images. 

We continue to get many questions about dew point and what is this new measurement and why is it replacing humidity.  Dew point has always been around and it is the measure of how much moisture in the atmosphere.  In order to calculate humidity, you need the air temperature and the dew point temperature; or the temperature water vapor in the atmosphere will condense and form dew. 

Like temperature, dew points are air masses that affect entire regions for a few days until a cold front or warm front moves through.  Dew points in the 40s and 50s is dry and comfortable air.  When dew points get into the 60s it starts to get damp, especially in the upper 60s.  Dew points in the 70s are considered tropical and it is very steamy out, and 80s are miserable and extremely rare. 

Milwaukee had a dew point of 80 in July..the first time since the heat wave of 1995.  To show you how humidity is misleading, if it is 90 with a dew point of 80, the humidity is 67%.  At 110 degrees and a dew point of 80, the humidity is only 33%, but trust me, it is very humid and hot!

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Milwaukee, WI

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Few Clouds
E at 3 mph

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