The First Half of August

July’s wet weather has continued over the first half of August.  With 12.17” of rain since July 1, Washington, D.C. has had an exceptionally wet summer despite the third driest June on record.  The amount of rain since July 1 makes the last six weeks the wettest period (12.17”) in Washington, D.C. since June-July 2015 (19.95”).  Washingtonians got 3.31” of rain on July 28 for their largest daily rainfall total since 2012.

Rain events in the Mid-Atlantic Region during the summer and fall can often be attributed to current or former tropical systems such as Floyd in 1999 or Irene in 2011.  While there have been eight tropical storms and two hurricanes in the Atlantic Ocean so far this season, none have directly impacted the United States.  But mid-August is when the hurricane season tends to get more active.  Ironically, the last six weeks have been exceptionally wet in the DC Metro Region without any tropical systems.  The wetter than average conditions have reduced Washington, D.C.’s ongoing rainfall deficit.

From August 1, 2015 through April 30, 2017, Washington, D.C. amassed a rainfall deficit of 13.75”, with 17 of those 20 months being drier than average.  However, both May and July were significantly wetter than average and that trend has continued during the first half of August.  That’s offset some otherwise drier than average months earlier in the year to give Washingtonians a rainfall surplus of 2.94” for the year.

The above average rainfall has also contributed to a cooler than average start to August.  Unlike last year, temperatures this month have been nearly a full degree cooler than average.  There have been five days of temperatures at 90°/+ over the first 17 days of August, compared to 13 such days last year.

A shift in the weather pattern will bring more summer-like temperatures to the Mid-Atlantic Region over the next week.  NOAA indicates a higher than average potential for cooler than average temperatures for the final week of August.  Scattered showers and thunderstorms are possible across the DC Metro Area on several days over the next week, so odds are that the trend of above average rainfall will continue as the end of meteorological summer approaches on August 31.