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Posted at 10:30 AM ET, 07/21/2009

Record Low Dew Point Last Week?

By Jason Samenow

* Showers? Full Forecast | NatCast | Dew Points for Dummies *

In this delightful D.C. summer, we've had numerous swell days with dew points in the 50s or lower. As a reminder, whenever dew points are in the 50s or lower in the summer here, the air is very dry and comfortable compared to dew points which are customarily in the sticky mid-to-upper 60s.

Last week, some of us dew point devotees noticed it drop down to the desert-like 30s on Tuesday. How rare is that in July in D.C.?

Keep reading for the answer...

Steve Zubrick, science operations officer at the National Weather Service in Sterling, Va., searched his hourly weather records dating back to 1977 and found that July dew points have only dipped into the 30s at Reagan National Airport (DCA) two other times.

Prior to last Tuesday's 39 at DCA (at 4 p.m.), the dew point fell to 39 on July 1, 2007 and also on July 1 in 1988, when it bottomed out at 37 degrees.

So the dry air we had last week was indeed rare -- something that only happens about once a decade it seems.

By Jason Samenow  | July 21, 2009; 10:30 AM ET
Categories:  Local Climate  
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