Recent June Weather Trends

Summer officially arrives in June and Washingtonians have experienced some of the hottest weather of the year over the course of the month.  June averages one 100° day roughly every five years in the Nation’s Capital.  Thirteen of the last 20 June’s have been warmer than average in Washington, D.C., following a period when 8 of 13 were cooler than average between 1992 and 2004.

June weather can be very streaky in the DC Metro Area.  June 1994 became DC’s hottest on record largely due to a 14-day heat wave with highs of at least 90° from June 13 – 26.  However, that was the longest heat wave of the 1994 summer with the hottest temperature during it being DC’s June 15 record high of 101°.  That would remain DC’s hottest temperature, overall, for more than three years until August 1997.

Fast forward 16 years to June 2010.  With 18 days of at least 90°, June 2010 supplanted 1994 as DC’s hottest June on record.  As many Washingtonians may recall, the summers of 2010, 2011 and 2012 were each exceptionally hot.  Triple-digit heat occurred in all three June’s, but not in the Nation’s Capital since 2012.

June is one of DC’s wetter months of the year, with a monthly average of 3.78” of rain.  Although June and July 2011 were each drier than average, August 2011 was significantly wetter than average.  That, in large part, was due to rainfall associated with Hurricane Irene.  It’s easy to get a significant amount of rain during the summer in the DC Metro Area because of current or former tropical systems.  June 1972 remains DC’s third wettest June due to the remnants of Hurricane Agnes. 

Despite recent strides, tropical systems are challenging to predict and any appreciable rainfall from one is atypical in this part of the country.  Therefore, Washingtonians shouldn’t expect any significant weather from a tropical system with any regularity in June.  Meanwhile, DC Area residents can see rainy summers much more frequently due to the position of the jet stream.  If the jet stream, a fast moving current of air in the atmosphere that helps steer weather systems, sets up in a particular way it can facilitate more frequent showers and thunderstorms. 

More typically, the dominant weather pattern in the Mid-Atlantic Region during the summer months is hazy, hot and humid weather with only isolated showers and thunderstorms.  That’s because the dominant weather feature for much of the eastern United States during the summer and early-fall is the “Bermuda High.”  That is a semi-permanent seasonal area of high pressure that pumps hot and humid air northward from the Deep South.  It also serves to suppress any widespread rainfall. 

June 2019 has gotten off to a relatively benign start in the Nation’s Capital with average temperatures through June 13 and a small rainfall surplus of 0.16”.  NOAA expects the next 8 to 14 days to be warmer and wetter than average in the DC Metro Area.  That means Washington, D.C. has a good chance to see its 10^th consecutive warmer than average June.