How Hot can the Summer be in Washington, D.C.?

Washington Monument  (Source: National Park Service)

Although summers in the Mid-Atlantic Region are known to feature hazy, hot and humid weather, triple digit heat is a rarity in the Nation’s Capital.  Given the unique geography of the region, it takes a rare set of circumstance for the thermometer to reach the century mark in Washington, D.C.  In fact, 100 degree temperatures only occur every few years in the Mid-Atlantic Region.  

That’s what helped make the summers of 2010 through 2012 so distinctive for Washingtonians.  Having one exceptionally hot summer in this part of the country would be memorable, but three consecutive blisteringly hot summers was unusual.  Prior to June 24, 2010, it hadn’t been 100 degrees in the Nation’s Capital since 2007.  What’s more, July 2010 featured three days of triple digit heat.  Also, what made the 2010 summer so memorable was the frequency of warmer than average weather.  The Nation’s Capital averages 36 days of at least 90 degrees or hotter in a given year, while 2010 saw 67 such days.  According to National Weather Service records, June 2010 was the warmest on record in Washington, D.C.

The earliest it has ever reached 100 degrees in the Nation’s Capital was on June 5, 1925.  However, that was measured downtown before National Airport opened in 1941.  Once National Airport opened, it became the official weather reporting site for Washington, D.C.  The earliest in the season it reached 100 degrees at National Airport was on June 9, 2011 when it was 102 degrees.  According to the National Weather Service, the latest in the season the temperature reached 100 degrees in Washington, D.C., was on September 8, 1939.  

The 2011 summer featured even more triple digit heat in the Nation’s Capital than 2010 did.  It was at least 100 degrees on five different occasions during summer 2011.  It was so hot in July 2011 that the Nation’s Capital set a new record for warmest month ever with an average monthly temperature (combining daily highs and lows) of 84.5 degrees.  July 2010 and July 1993 tied for the previous record with an average temperature of 83.1 degrees.

Little did Washingtonians realize that the four days of triple digit heat in 2010 and the five such days in 2011 represented an upward trend leading toward the summer of 2012.  The summer of 2012 featured eight days of triple digit heat.  The temperature reached 105 degrees at National Airport on July 7, 2012 – the hottest temperature observed in the Washington, D.C. since August 1997.  July 2012 also became the second warmest month on record in the Nation’s Capital with an average monthly temperature of 84 degrees.  

Following last month – the warmest May on record – we’ll have to see if this summer more closely resembles the torrid summers of 2010 through 2012 or last summer which featured closer to average temperatures.  It hasn’t been 100 degrees in Washington, D.C., since July 26, 2012.