What’s Memorable about Summer 2017?

Great Falls, Maryland

Meteorological summer is comprised of the months of June, July and August.  These three months couldn’t have been more different in the Nation’s Capital this year.  To begin, the summer of 2017 was warmer than average, with an average temperature of 78.8° (as compared to 77.7°).

Washington, D.C.’s hottest temperature of the summer was 98° on July 20, 2017.  By comparison, last year’s hottest temperature was 101° on August 13.  The longest heat wave of 2017 was six days – from July 17 – 22.  A “heat wave” is defined as a minimum of three consecutive days with temperatures 90°/+.  Washington, D.C. averages 36 days of 90° heat in an entire year.  There were 37 days of 90°/+ temperatures at National Airport (DCA) just this summer.  This year’s first day of 90° heat came on April 29, while last year’s first 90° day didn’t occur at DCA until June 11. 

This summer’s coolest temperature was 56° on June 8.  Unlike 2016, when September featured seven days of 90°/+, it hasn’t been 90°/+ in Washington, D.C. since August 22 (92°).  Part of that can be attributed to just how wet the summer was.  While June 2017 was the third driest on record in the Nation’s Capital, the proverbial floodgates opened in July.  The most rain fell at National Airport in July (9.15”) since 1969.  August 2017 was also wetter than average and that led to a seasonal total of 14.86” from June 1 through August 31 (4.42” wetter than average).

In fact, five of the last six summers have been wetter than average in Washington, D.C.  Sometimes the remnants of tropical systems bring appreciable rainfall to the Nation’s Capital.  However, in the last six years only the summer of 2011 saw any rainfall from tropical systems in the Mid-Atlantic Region.  That’s when Hurricane Irene made landfall in North Carolina and brought the DC Metro Area some much-needed rainfall.

Does a warmer and wetter than average summer foreshadow a colder and snowier than average winter?  No correlation can be drawn between the two.  There have been instances of hot and dry summers (1995) followed by snowier than average winters (1995-1996).  Conversely, Washingtonians experienced their second hottest summer on record in 2011 (that was also wetter than average), but the 2011-2012 winter saw less than 15% of the average annual snowfall (15.4”).  September remains the most active month of the hurricane season which continues through November, so we still have some time to go before thinking about winter.