How Hot Has August Been?

August is well positioned to finish as one of the warmest of all time in the Nation’s Capital – and that’s following the sixth warmest July on record.  The first half of August broke a slew of hot weather records across the Mid-Atlantic Region and northeastern United States.  Washington, D.C. has had four days of triple-digit heat this summer, including three consecutive days from August 13 – 15.

Since just one day of triple-digit heat is infrequent in the Nation’s Capital, having three consecutive days of 100 degree heat is quite remarkable.  In fact, this week’s streak of temperatures at/above the century mark ties it for the second longest streak on record.  The longest streak of consecutive days at/above 100 degrees in Washington, D.C. is four days and occurred most recently on July 5 – 8, 2012, according to the National Weather Service.  

This week’s stretch of three consecutive days above 100 degrees was the longest such streak to occur in August since 1930.  You have to go back to 1997 to just get consecutive August days at/above 100 degrees in Washington, D.C.  By coincidence, the second of two consecutive 100 degree days occurred 19 years ago today when Washingtonians sweated through a record high of 105 degrees.  The combination of record high temperatures and uncharacteristically high humidity creates particularly dangerous heat that necessitates heat advisories and excessive heat warnings. 

No records are kept of “heat index” temperatures – the “feels-like” temperature when you combine temperature and relative humidity – but the heat index in the Nation’s Capital in the last week has rivaled the 122 degree heat index that occurred on July 16, 1980.  More recently, on July 22, 2011, the heat index reached 121 degrees.  Those dates are two of the highest observed heat index temperatures in Washington, D.C.  

Since July 24, Washingtonians have endured seven days of low temperatures at/above 80 degrees, producing six record high low temperatures and tying the 2011 record.  Such warm overnight temperatures have contributed to an average monthly temperature (combining daily highs and lows) of 83.8 degrees in Washington, D.C. through August 16.  This is significantly warmer than the 78.1 degree average at National Airport. 

Records kept by the National Weather Service indicate another unprecedented event happened this summer.  There have been two streaks of at least seven consecutive days with temperatures at/above 95 degrees – from July 22 – 28 and the current streak that began August 10.  Yesterday was also the sixth consecutive day of at least 97 degrees in Washington, D.C. which ties for second longest streak since 1953.  Fortunately, starting tomorrow there is going to be a change in the weather pattern with an end to the extreme heat in the Mid-Atlantic Region.

Washington, D.C.’s Warmest Augusts (Degrees Fahrenheit - Source: NWS)

1.  82.8 (1980)

2.  81.3 (1995), (1978)

4.  81.1 (2002)

5.  81.0 (2012, 1983)

7.  80.7 (1988)

8.  80.6 (2006)

9.  80.3 (1959)

10.  80.2 (2010)