Lots of Rain

June has continued D.C.’s wetter than average trend that began in April.  The above average rainfall has been quite beneficial after a drier than average start to the year.  With a week left in June, it’s an open question of how much wetter than average this month will end up being in the Nation’s Capital.

 

According to the National Weather Service, Washington, D.C. had 24 drier than average months in the 31-month period from August 2015 through March 2018.  That led to a rainfall deficit of 16.42” of rain during that time period.  That’s why the last three months of above average rainfall has been generally welcome.  The last time three or more consecutive months had above average precipitation in Washington, D.C. was February 2014 through August 2014.

The calendar years of 2016 and 2017 were both several inches drier than average in the Nation’s Capital.  In addition, had it not been for D.C.’s second wettest June on record in 2015, that would have otherwise been a drier than average year as well.  Given the generally dry weather pattern the last three years, June 2015 can be considered an anomaly.

D.C.’s 31-month rainfall deficit that stood at 16.42” on April 1, 2018 has fallen to 8.92” through June 22.  So far in 2018, Washingtonians have a rainfall surplus of 6.24” as officially measured at National Airport.  Since April 1, there have been six different days with at least one inch of rain in the Nation’s Capital.  Such significant rainfall totals have led to localized flooding in parts of the Mid-Atlantic Region.  The most destructive flooding occurred on May 27 in Ellicott City, Maryland after a slow-moving complex of thunderstorms produced a few inches of rain.

From April 1 through June 22, D.C. residents got 17.32” of rain.  This is nearly 44% of what Washington, D.C. averages for an entire year !  That’s remarkable because it occurred without the heavy rain that a tropical system would bring.  

An extended period of time with wetter than average weather is exactly the type of pattern that’s ideal to make up a rainfall deficit.  As we’ve seen, too much rain all at once is not a good thing for flood prone communities.  NOAA expects near average precipitation in the D.C. Metro Area during the month of July.