August in Washington, D.C.

August is the third and final month of “meteorological summer” and remains quite warm in much of the United States.  However, Washingtonians eager for the cooler weather of fall, should like August’s downward progression of average temperatures.  Washington, D.C.’s average high and low temperatures on August 1 are 88 and 71 degrees, respectively, while they fall to 84 and 68 degrees by month’s end.  Official weather observations for Washington, D.C, are measured at National Airport.   

The highest annual average high temperature in Washington, D.C. is 89 degrees from July 7 through July 22.  After that, average temperatures start to decline.  At the same time, hours of daylight continue to contract during the month of August.

August can still be quite hot in Washington, D.C. with triple-digit heat occurring during five different years since 1997.  For example, the 105 degree temperature on August 17, 1997 is the hottest temperature on record at National Airport (it occurred again more recently on July 7, 2012) according to the National Weather Service.  However, the hottest temperature on record in the Nation’s Capital is 106 degrees which occurred twice before National Airport opened in 1941.  

By comparison, the coolest temperature on record during the month of August in Washington, D.C. is 49 degrees, which occurred most recently on August 29, 1986.  Thirteen of the last 20 Augusts have been warmer than average in Washington, D.C. The longest heat wave of 2016 continued yesterday with a high temperature of 91 degrees.  That was the 13^th consecutive day at or above 90 degrees and the 30^th of 2016.  Washington, D.C. averages 36 days at or above 90 degrees for the entire year.

August averages 3.44” of rain.  The wettest August on record in Washington, D.C. was in 1928 when 14.41” fell.  On the opposite end of the spectrum, Washington, D.C.’s driest August was in 1962 when just 0.55” of rain fell.  Decaying tropical systems sometimes impact the Mid-Atlantic Region in August, such as Hurricane Irene in 2011.  It brought the Nation’s Capital beneficial rain after initially making landfall in North Carolina’s Outer Banks.  NOAA’s outlook for August calls for an equal chance of above or below normal temperatures and precipitation in the Mid-Atlantic Region.  That means near average conditions can be expected in the Nation’s Capital this month.