Fall Takes Over

Glen Echo Park, Glen Echo, Maryland

It was hard to imagine a few short weeks ago that the cooler, fall-like weather would be here by this point in September.  That’s because this month got off to an exceptionally hot start with seven of the first nine days in the 90s.  However, by comparison, today’s average high is only 75 degrees at National Airport – where weather measurements are made for Washington, D.C.

Although the weather has gotten much more fall-like since the hot start to September, it has remained relatively dry for Washingtonians.  This month has had only 0.5” of rain through yesterday.  Since August 1, the rainfall deficit in the Nation’s Capital has grown to more than 4.5”.  The dry conditions have contributed to many brown lawns and dry leaves falling off trees across much of the DC Metro Region.

Unlike past Septembers, the Mid-Atlantic Region hasn’t seen any rainfall from decaying tropical systems.  Over the last twenty years there have been some very wet Septembers due to the remnants of former hurricanes and tropical storms.  The remnants of Fran came in September 1996, while Hurricane Floyd brought appreciable rainfall to the Nation’s Capital in September 1999.  Most will remember Hurricane Isabel in September 2003, which caused widespread power outages due to the high wind associated with the weakening tropical system. 

According to the National Weather Service, 2011 was the last September when the Mid-Atlantic Region had any impacts from a decaying tropical system.  The remnants of Tropical Storm Lee helped make September 2011 one of the wettest on record in the Nation’s Capital.  That goes to show that a tropical system doesn’t have to be especially strong to cause major impacts.
 

Although this month has been significantly drier than average, it isn’t near the record.  September 2005 was the driest on record in the Nation’s Capital when only 0.11” of rain fell (compared to the September average of 3.72”).  However, that was followed by the wettest October on record in Washington, D.C.

This month has had a total of seven 90 degree days in the Nation’s Capital, which is the highest monthly total since September 2010 when there were ten such days.  The hottest temperature this month was 96 degrees on September 3, while the coolest temperature in the Nation’s Capital was 55 degrees on September 14.  The warm start to the month has put this September in a good position to finish among the warmest on record in the Nation’s Capital.  Fortunately for those ready for autumn, no extreme heat is in the forecast locally.  My colleagues and I on the WUSA9 weather team will keep you apprised of the latest weather forecasts.