Some Perspective on August 2017

The wetter than average summer in the Nation’s Capital continued during August, which will finish cooler and wetter than average.  This is the third cooler than average August in the last five years.  However, it’s only DC’s third wetter than average August in the last 10 years. 

The hottest temperature Washingtonians experienced this month occurred on August 22 (92°) while the coolest temperature this month was 62° on August 30.  The low temperature of 62° was the coolest temperature in the Nation’s Capital since June 28 (61°).  By comparison, Washington, D.C.’s average high and low temperatures on August 31 are 84°/68°.

This August’s cooler than average weather is in stark contrast to last August, which was the second hottest on record in Washington, D.C.  August 2016 had 23 days at 90°/+ (including three days of 100° heat), while there have been only 9 days at 90°/+ this month.  Last August’s average temperature (combining daily high and low temperatures) was 82.7° compared to this month’s average temperature (through August 30) of 77.4° (below August’s average monthly temperature of 78.1°).

There has been 4.58” of rain this month with the bulk of that occurring on August 7 (1.47”) and August 29 (0.98”).  Three of the last four months have been wetter than average in the Nation’s Capital.  That’s paid dividends in offsetting much of the rainfall deficit that Washington, D.C. incurred during a very dry period from August 1, 2015 through April 30, 2017. 

In fact, Washington, D.C. has a rainfall surplus of 4.51” since the start of meteorological summer on June 1 and a rainfall surplus of 3.34” since January 1.  A large portion of that rainfall surplus came last month in what was DC’s wettest July (9.15”) since 1969.  Unlike past summers, Washingtonians haven’t experienced any rainfall from current or former tropical systems.  However, that is poised to change as the remnants of Hurricane Harvey are expected to bring the Mid-Atlantic Region some rain tomorrow night and Saturday.