DC’s Return to Summer?

 

 

 

The Nation’s Capital had an average monthly temperature more than 1° below average through the first 11 days of September.  However, temperatures have warmed to more summer-like levels so far this week, with today’s temperatures poised to be warmer than average for a fourth consecutive day.

Monday was the first 90° day in the Nation’s Capital since August 30.  Following a high of 89° yesterday, highs today could once again reach 90° this afternoon.  That’s not unusual as September has featured summer-like weather for Washingtonians in recent years.  Three of D.C.’s five warmest Septembers on record have occurred over the last decade, according to data from NOAA. 

Not only has September been a warmer than average month more often than not over the last decade, there have also been large fluctuations in rainfall.  September rainfall in Washington, D.C. can vary significantly from one year to the next depending on whether or not tropical systems impact the Nation’s Capital.  For example, the remnants of Tropical Storm Lee (2011) and Hurricane Florence (2018) each contributed toward giving Washingtonians two of the 10 wettest Septembers on record.

With the exception of 1.34” of rain at National Airport on September 1, due to the remnants of Hurricane Ida, this has been a dry month with a combined rainfall total of only 0.26”.  Shower and thunderstorm potential exists in the D.C. Metro Area in the coming days, but given the scattered nature of showers and thunderstorms, it’s possible that no significant rainfall will occur at National Airport before the end of the week. 

My colleagues and I on the WUSA9 Weather Team are expecting a largely dry weather pattern to return to the D.C. Metro Area this weekend and continue into early next week.  With a combined total of only 1.60” of rain over the last two weeks, the second half of the month will have to be fairly wet in order for September 2021 to finish with at least an average amount of rainfall. 

NOAA recently updated its monthly climate statistics to reflect the 30-year period of 1991-2020 (replacing the 1981-2010 data set).  September became an even wetter month with the updated statistics showing a monthly rainfall average of 3.93” (compared to 3.72” previously).