DC’s Strange May 2021 Weather

 

A Beautiful Day at the Avenel Park, Potomac, Maryland

May is poised to finish as a cooler than average month in Washington, D.C. for a second consecutive year.  That’s the first time there have been back-to-back cooler than average May’s in the Nation’s Capital since 2008-2009.

DC’s weather has been very streaky this May with 14 of the first 18 days cooler than average.  That’s given this month an average temperature (combining daily high/low temperatures) nearly 3° cooler than average through May 18.  Washingtonians then experienced weather more characteristic of mid-summer with highs in the 90s on four out of seven days between May 20 and May 26.  The very warm week in the Nation’s Capital led DC’s average monthly temperature to soar from being 2.7° below average on May 18 to within 0.5° of average on May 27. 

Temperatures plummeted, however, over the weekend.  DC’s high temperatures of 59° and 58°, respectively, on May 28 and May 29 were more characteristic of mid-to-late March than Memorial Day Weekend.  While not quite record-setting in the Nation’s Capital, record low-high temperatures were set at both Dulles and BWI Airports.  Today’s high temperatures have rebounded to the 70s, but that won’t be enough to prevent May 2021 from finishing as a cooler than average month overall.  

That shouldn’t come as much of a surprise, though, as temperatures have been cooler than average on 19 of May’s 31 days in Washington, D.C.  It won’t be as cool as last May was in the Nation’s Capital as temperatures will finish nearly a degree cooler than average this month, while May 2020 finished more than 2° below average.  That can largely be attributed to the fact DC had four days of 90° heat this month, while last May didn’t have any.

Despite more than 3” of rain in the Nation’s Capital over the last week, May 2021 will still finish with below average rainfall.  That’s the result of the very dry first portion of the month, which had a combined total of only 0.69” of rain through May 23.  Washington, D.C. is now poised to finish with 3.77” of May rainfall.  Fortunately, following the rainy and cool last few days, Washingtonians are in store for a sunnier and milder start to the week.  The National Oceanic and Atmospheric Administration (NOAA) expects warmer than average June temperatures in the DC Metro Area with near average rainfall.