A Harbinger of Summer ?

NOAA's Temperature Outlook for July 2018

The Nation’s Capital has had a considerable amount of record June heat over the last 10 years.   June is also D.C.’s second wettest month of the year on average behind only May.  This June has been warmer and wetter than average in the Nation’s Capital.  Some may wonder if that foreshadows similar weather for the rest of the summer.  There are a few summers to look at for clues.

June 1994 was D.C.’s second hottest on record and featured a 14-day streak of 90° temperatures.  That was the hottest stretch of the entire 1994 summer and contributed to making June warmer than August.  Since June’s average monthly temperature in DC is nearly three degrees cooler than August, it’s rather unusual for June to be warmer than August.  June 1994 was also much drier than average with a monthly total of 1.59”, compared to the average of 3.78”.  While the summer of 1994 was drier and warmer than average in its entirety, July and August were closer to average than June 1994 was.

Washingtonians experienced the wettest June on record in 2006 with 14.02” of rain and was D.C.’s wettest month since August 1955.  The frequent rainfall also contributed to make June 2006 a slightly cooler than average month.  By comparison, the rest of the 2006 summer was drier and warmer than average in the Nation’s Capital.

Washingtonians experienced the second wettest June on record (11.94”) in 2015.  In a rare combination, June 2015 was also warmer than average with an average monthly temperature of 78.1°.  D.C. had 12 days with high temperatures in the 90s in June 2015, compared to an average of seven to eight such days since 1993.  While July 2015 was also wetter and warmer than average, August 2015 was drier and warmer than average.  In other words, there was no summer-long pattern.

This should help illustrate that while June’s dominant weather patterns can sometimes continue for much of the summer, June’s weather isn’t a reliable predictor of what the entire summer will be like.  One final example: the summer of 2011 was one of D.C.’s hottest on record and was also poised to be one of the driest as well.  However, the remnants of Hurricane Irene brought the D.C. Metro Area significant rainfall on August 27-28, 2011.  Consequently, August 2011 finished as D.C.’s wettest August since 1967.  NOAA expects this July to be warmer than average with near average precipitation in the D.C. Metro Area.

NOAA's Precipitation Outlook for July 2018