Below Freezing Temperatures in Washington, D.C.

Today is the coldest December day in the Nation’s Capital since 2010.  By coincidence, six years ago today was the last time high temperatures remained at or below freezing in December (27 degrees).  Today’s average high temperature is 46 degrees, so having a high temperature only near 30 degrees is truly remarkable.

The temperature fell to 17 degrees early this morning at National Airport, making it the first December morning since December 22, 2008 that temperatures fell below 20 degrees there (16F).  Meanwhile, a record low temperature of 9 degrees was set at Dulles Airport (breaking the old record of 10 degrees from 1989).  Having such frigid temperatures absent a fresh snowpack is a testament to just how frigid this air mass is.

National Weather Service data provides a good snapshot of how rare it is for high temperatures to remain at or below the freezing mark in Washington, D.C.  December averages approximately 1.4 such days, January 4.6 days, February 2.3 days and March one sub-freezing day roughly every two or three years.  Winter’s seasonal average temperature in Washington, D.C. is 38.2 degrees, but the recent cold winters of 2013-2014 (37.4F) and 2014-2015 (36.5F) were below that.

January 2004 is significant because there were 15 days that month when temperatures remained at or below freezing in the Nation’s Capital (the highest such total in the last 25 years).  You have to go back to 1989, though, for the benchmark on just how cold the month of December can be in Washington, D.C.  With a monthly average temperature of 27.9 degrees, that remains the coldest December since 1917.  Record low high temperatures were set on three consecutive days on December 22-24, 1989, with a record low of 7 degrees on December 23.  That was the last time temperatures fell to the single digits during the month of December in Washington, D.C.  

Although Washingtonians have escaped the snow that has already accumulated this month in Chicago, Cleveland and Buffalo, the extreme cold arrived here yesterday.  Having approximately 48 hours of such frigid weather will help surface temperatures fall to at or below freezing in many areas across the DC Metro Region, especially those unpaved areas like grassy surfaces and cars parked outdoors.  

This will help create the potential for slippery conditions along with the potential of some freezing rain and sleet late tonight and early tomorrow morning in areas from the DC Metro northward toward the Mason-Dixon Line.  My colleagues and I on the WUSA9 Weather Team will keep you posted, on-air, online and on the free WUSA9 mobile app.