Final Month of Summer

Strong to Severe Storms a "Slight" Risk in parts of the Mid-Atlantic  (Source: NOAA)

July 2019 was DC’s third consecutive wetter than average July.  While not as wet as 2017 or 2018, this July still finished with 6.49” (almost double the monthly average of 3.73”).  Although no record highs were set, Washingtonians endured 22 days of 90° heat in July, which finished with an average temperature of 82.1°.  That left last month tied with July 1955 for DC’s ninth warmest on record.

August has gotten off to a warm and relatively dry start, with no measurable rainfall yet at National Airport – DC’s official weather reporting site.  That’s not to say parts of the DC Metro haven’t had appreciable rainfall so far this month.  A thunderstorm last evening in Bethesda, Maryland, was its first significant rainfall in more than a week.  The Nation’s Capital averages 2.93” of rain in August.  Ten of the last 20 August’s have been wetter than average, including the last two.

The tropical Atlantic often gets busier during the month of August.  Such was the case in 2011 when a weakening Hurricane Irene brought a few inches of rain to the Nation’s Capital after its landfall in North Carolina.  August can also been a very dry month in Washington, D.C., such as in 1995 and 1998 when less than an inch of rain occurred during the entire month.  In fact, August 1998 ranked as DC’s second driest on record with only 0.59” of rain.

August is the third and final month of “meteorological summer” that began June 1.  Fourteen of the last 20 August’s have been warmer than average in the Nation’s Capital.  To add to that, August has been warmer than July in the Nation’s Capital in eight of the last 20 years.  That’s pretty remarkable considering DC’s average August temperature (combining daily high and low temperatures) is nearly 2° cooler than July (78.1° vs. 79.8°).  Its hottest August temperature on record is 106°, recorded on August 6, 1918 and also on July 20, 1930 – DC’s hottest overall temperature. 

DC’s coolest observed August temperature is 49° and has occurred three times, most recently on August 29, 1986.  Although triple-digit heat typically occurs only every few years in the Nation’s Capital, it happens more frequently than temperatures less than 60°.  DC residents experienced 100° August heat as recently as 2016.  Meanwhile, August temperatures haven’t fallen below 60° in Washington, D.C. since 2004.  NOAA expects this August to finish with near average temperatures and rainfall in the DC Metro Region.