Final Month of Meteorological Summer

This summer has been quite unique in the Nation’s Capital.  June was the third driest (1.13”) since 1871 and was the eighth consecutive warmer than average June.  Washingtonians, then, experienced their seventh wettest July (9.15”), and wettest since 1969.  At least 0.65” of rain occurred at National Airport on five separate July days, while an inch or more fell on two other days.

The 3.31” rainfall on July 28 not only set a daily rainfall record for July 28 in Washington, D.C., but was also the first time at least 3” of rain occurred in a single day in nearly five years.  Some may recall that 4.84” of rain fell from October 28 – 30, 2012 when the remnants of Hurricane Sandy affected the Mid-Atlantic Region.  Most of that total occurred on October 29 when 3.85” fell at National Airport.

That helps illustrate how rare 3” rainfall totals are in the DC Metro Area, especially outside of current or former tropical systems.  Dulles Airport saw its wettest July on record (8.80”) last month, dating back to 1963.  The wetter than average final week of July also contributed to cooler than average temperatures.  That caused July to go from being the third warmest on record July 25 (83.3° average monthly temperature), to twelfth warmest (81.7°).  

August is the third and final month of “meteorological” summer that spans from June 1 through August 31.  Average high and low temperatures in Washington, D.C. range from 88°/71° on August 1 to 84°/68° on August 31.  The National Weather Service says Washingtonians can expect an average of 2.93” of rain this month.  That’s DC’s first monthly average under 3” since February (2.62”).  A significant change between July and August, though, is that the tropics tend to heat up quite a bit during the month of August, so any rainfall in the Mid-Atlantic Region could be influenced by tropical systems.

August 2016 was the second warmest on record in the Nation’s Capital.  Although two of the last three months have been wetter than average, the DC Metro Area has been significantly drier than average, overall, dating back to August 1, 2015.  However, NOAA expects near average temperatures and precipitation in August for much of the eastern United States.