Just how Warm was July 2015 in the Nation's Capital?

Cooling off at the beach, Pasadena, MD

July’s average monthly temperature of 81.5 degrees (combining daily highs and lows) has made it the hottest month in the Nation’s Capital since July 2012.  That also happens to be the last time any triple digit heat occurred in Washington, D.C.

July 2015 featured 14 days with temperatures of 90 degrees and concluded with Washington, D.C. in the midst of its longest heat wave of the summer.  Daily high temperatures have been at least 90 degrees since July 24 and are expected to continue to be at least that warm well into next week. 

Meteorologists define a “heat wave” as any three-day period with temperatures of 90 degrees or hotter.  So, with a running total of 8 such days we have exceeded the minimum definition by a considerable margin.  The previous longest heat wave of the summer was a six-day stretch in June.  If the forecast comes to fruition the next few days, Washingtonians will see their longest heat wave since the summer of 2011.

The hottest temperature to occur in the Nation’s Capital this year was 98 degrees on July 19, while July’s coolest temperature measured at National Airport was 66 degrees.  Longtime Washingtonians may remember the summer of 2000 as being significantly cooler than average.  That was also the coolest July on record at National Airport with a monthly average temperature of 74.7 degrees.  According to the National Weather Service, July 2015 was also wetter than average with a monthly total of 5.01” of rain at National Airport compared to an average of 3.73”.

As we turn the calendar to August, will the warmer and wetter than average weather continue in the Mid-Atlantic Region?  The Climate Prediction Center is calling for near average temperatures during the month of August in this part of the country.  However, triple digit heat has occurred as recently as 2011 during the month of August, so we’ll have to see what happens.  Fortunately, my colleagues and I on the WUSA9 weather team don’t have any triple digit heat in the forecast during the next seven days.