August: Final Month of Meteorological Summer

NOAA's August Temperature Outlook

Meteorologists consider June, July and August to be “the summer months.”  Not only were June and July warmer than average in the Nation’s Capital, but they were also much wetter than average.  The second half of July 2018 was the wettest on record in Washington, D.C.  This is remarkable since all of the rainfall (9.73” at National Airport) occurred without any tropical systems. 

The month of August averages 2.93” of rain in Washington, D.C., according to NOAA.  August 2018 has gotten off to a wet start with 1.28” of rain over the first two days or almost half of the monthly average.

The month of August is the second hottest of the year in Washington, D.C. with an average temperature (combining daily high and low temperatures) of 78.1°, behind only July’s average of 79.8°.  Fourteen of the last 20 Augusts have been warmer than average in the Nation’s Capital.  Average high and low temperatures fall throughout the month of August, ranging from 88°/71° on August 1 to 84°/68° on August 31. 

DC’s record high temperature for the month of August is 106° that occurred on August 6, 1918, while the coolest observed temperature is 49°.  DC has been as cool as 49° a total of three times in August; most recently on August 29, 1986. 
 

As Washington, D.C. has grown and developed in recent decades, there has been a disproportionally higher number of record high temperatures than record lows due to an increased “urban heat island effect.”  Over the last 10 years, the Nation’s Capital has tied or set a total of 13 record high temperatures (including record high-low temperatures).  That’s compared to only one record low-high temperature over the same time period.  A “low-high temperature” record often means it was a much cooler than average day, while a “high-low temperature” means it was an unusually warm day. 

NOAA expects near to slightly warmer than average temperatures this month in the Nation’s Capital.  August is also predicted to be a wetter than average month.

NOAA's Precipitation Outlook for August