Say Good-Bye to Warm and Dry Weather?

View of Key Bridge and Georgetown from Roosevelt Island

Residents of the Mid-Atlantic Region have surely noticed area lawns and gardens have been struggling in recent weeks.  That can be attributed to the frequent record heat since early July, combined with a growing rainfall deficit.  Following the sixth warmest July and second warmest August on record, September has seen more of the same.  

Through September 18, the Nation’s Capital has had six days with high temperatures in the 90s this month, including four days of at least 95 degrees.  Washingtonians also experienced their hottest September day since 2010 when it reached 98 degrees at National Airport on the September 8.  While it has averaged over three days of 90 degree heat in September since 1993, the Nation’s Capital has averaged just under one day at or above 95 degrees over the same period.  So, having four such days this month is rather remarkable.

Dating back to last September, nine of the last 12 months have had below average rainfall in Washington, D.C.  Not since May has there been a month with above average rainfall in the Nation’s Capital.  To add to that, this month has had only 0.05” of rain so far.  Washington, D.C. has a rainfall deficit of 4.48 inches since March 1 and Dulles Airport’s deficit is 4.84 inches.

The combination of prolonged above average temperatures combined with below average rainfall have led to “abnormally dry” conditions across much of Virginia and North Carolina according to the National Drought Monitor Index.  Conditions are more extreme in the northeastern United States, where a significant portion of New York and New England are experiencing severe drought.   

Although D.C. area gardens and lawns have gotten quite dry, the water tables are in good shape.  Hot and dry summers aren’t uncommon in this part of the country.  The summer of 1999 was very similar to this summer in the Nation’s Capital.  In fact, 1999 was so dry that parts of Virginia, Maryland and Washington, D.C. had water restrictions.  Fortunately, the remnants of Hurricane Dennis and Floyd brought an abrupt end to the dry conditions in September 1999.  

Historically, Washingtonians experienced their driest September in 2005 when only 0.11” of rain fell during the entire month; and that was followed by its wettest October.  This helps illustrate that the current dry conditions could change quickly.  This year’s rainfall deficit isn’t especially large or insurmountable.  My colleagues and I on the WUSA9 weather team are monitoring the prospect for rainfall tonight and tomorrow across much of the Mid-Atlantic Region.