Unofficial Start of Summer

Last month was wetter and warmer than average in Washington, D.C.  It finished with 4.97” of rain (nearly an inch above average) and was also DC’s seventh warmest May, with an average temperature of 71° (5° above average).  Since April 2018, 14 of the last 16 months have been wetter than average in Washington, D.C.  In that time, the Nation’s Capital has accrued a rainfall surplus of 29.87”.

June, July and August make of “meteorological summer.”  On the other hand, astronomical summer doesn’t get underway until the summer solstice later this month.  Temperatures continue to rise throughout the month of June in the Nation’s Capital, going from average high and low temperatures of 80°/62° on June 1 to 88°/70° on June 30.  The hottest June temperature on record in Washington, D.C. occurred relatively recently when it was 104° on June 29, 2012.  That was also the last time 100° heat occurred in the Nation’s Capital during the month of June.  DC’s earliest 100° temperature was on June 5, 1925.  DC’s coolest June temperature on record is 43° (June 2, 1897).  

According to NOAA, 13 of the last 20 June’s have been warmer than average in Washington, D.C., including every June since 2010.  There have also been a total of 13 record high June temperatures in Washington, D.C. over the last 20 years.  That’s in addition to 21 record “high-low” temperatures.  In other words, on 21 occasions DC’s daily low temperature was at a record high level.  By comparison, there have only been two record “low-high” temperatures in the last 20 years and none since 2003.  That means that on two occasions daily high temperatures were much cooler than average.  Washingtonians haven’t had a record low temperature in June since 1979.

Washington, D.C. averages 3.78” of June rainfall, making it the second wettest of the year.  In the Nation’s Capital, 13 of the last 20 June’s have been wetter than average.  That includes three of DC’s five wettest June’s on record (2006, 2013 and 2015).  On the other hand, June 2017 was DC’s third driest with only 1.13”.  Decaying tropical systems have brought the DC Metro Area appreciable rainfall.  For example, June 1972 remains DC’s third wettest largely due to the impressive rainfall totals from remnants of Hurricane Agnes.  

NOAA currently expects an equal chance for above or below average temperatures and rainfall this month in the DC Metro Area.  That means Washingtonians can expect near average temperatures and precipitation this month.