D.C.'s Unusual June Weather

 

 

This is the first June that DC’s average temperatures and rainfall are based on NOAA’s updated climate data for the 30-year period of 1991-2020 that replaced the previous data set based on 1981-2010.  Since that change was made, DC’s average temperatures are warmer and the average rainfall is higher. 

At National Airport, the official weather reporting site for Washington, D.C., this June has been a relatively mild month.  There has only been one heat wave so far this year from June 5 – June 7.  Through June 26, there have only been four days with highs in the 90s.  That’s compared to six days this month high temperatures remained in the 70s.

That’s unlike some recent June’s that have featured a significant amount of extreme heat.  As recently as 2015, Washingtonians experienced 12 days of 90° June heat and the month finished nearly 2° warmer than average.  By comparison, June 2009 had only two 90° days and finished nearly 3° cooler than average.  While temperatures have been near average so far this month, June 2021 should finish as a warmer than average month overall.  My colleagues and I on the WUSA9 Weather Team expect DC’s second heat wave of 2021 to get underway today with a high of 90°.  This June will finish with a heat wave in the Nation’s Capital for a third consecutive year.

This month is also the wettest month of 2021 in Washington, D.C. with 5.48” of rain through June 26.  While more than one inch above DC’s June average of 4.20”, it doesn’t come close to some extremely wet June’s in the Nation’s Capital.  For example, three of DC’s five wettest June’s on record occurred in 2006, 2013 and 2015.  June can also be a very dry and hot month in Washington, D.C.  Such was the case in 2017 when only 1.13” of rain fell and the month finished one degree warmer than average.

June 2021 will likely finish as a warmer and wetter than average month in the Nation’s Capital.   Is that a harbinger of what the rest of the summer’s weather might be like?  The short answer is no.  It only takes one significant heat wave to produce a warmer than average summer month, or one tropical system to make the month wetter than average.  Conversely, the absence of those things could lead to near average temperatures and rainfall.  NOAA’s Climate Prediction Center expects a higher than average probability for a warmer and wetter than average July in the D.C. Metro Region.