Dog Days of Summer

The Nation’s Capital has experienced some of its most significant heat waves in August.  It was just two years ago that Washingtonians endured an 12-day heat wave that included three consecutive days of triple-digit heat (August 13 – 15, 2016).  That was the first time the District had such an occurrence since July 5 – July 8, 2012.  DC residents also experienced two days of triple digit heat in August 1997 and August 2002.

Local residents who are tired of the current hazy, hot and humid weather should take comfort in the fact that average temperatures fall during August.  The amount of daylight also falls during August.  The combination of a gradual decline in average temperatures and average amount of daylight are a sure sign of the approaching autumn.  

However, August 11 can still be a very hot day.  This date’s average high/low temperatures in Washington, D.C. are 87°/70°.  While the record high is 101° that occurred in 1900, today’s record low of 56° occurred in 1879.  Weather records in the Nation’s Capital date back to the 1870s. 

Over the last 30 years, Washingtonians have experienced wide variety of weather on today’s date.  Today’s record high-low temperature occurred in 2010 when DC’s low temperature on August 11 was a balmy 80°.  A record “high-low” temperature essentially means the coolest temperature of a given day was much warmer than average.  By comparison, today’s record low-high temperature of 69° occurred most recently in 1989.  A record “low-high” temperature means it was appreciably cooler than average on a particular day.  In this case, the high temperature was 18° below average.

Torrential rainfall has also occurred during slow-moving thunderstorms, which can sometimes lead to flooding.  That’s what happened on August 11, 2001 when 0.92” fell at National Airport and 1.6” fell at Dulles Airport.  Moreover, 3.79” of rain swamped the WUSA9 weather terrace and flash flooding occurred in parts of the DC Metro Area. 

Two years earlier on August 11, 1999, water restrictions went into effect in parts of the DC Metro Area during what had been a very hot and dry summer.  Ironically, there was a 180° shift in the weather pattern that helped end the dry conditions of that summer.  The remnants of Hurricane Dennis brought the DC Metro Area appreciable rainfall and that was followed by weakening Hurricane Floyd the following month.  More recently, Washingtonians saw record rainfall from Hurricane Irene in August 2011.