D.C.’s Pivot Toward Fall

 

Great Falls National Park, Maryland  (September 2020)

Average daily high and low temperatures today are 83°/67° in the Nation’s Capital.  But, September 2022 has gotten off to a warmer than average start in Washington, D.C.  NOAA’s Climate Prediction Center Prediction Center expects that to continue over the next one to two weeks.

There have already been two days with highs in the 90s so far this month.  Washington, D.C. has averaged three to four September days with highs in the 90s over the last 30 years.  The 90° warmth so far this month has made it the 11^th consecutive September with 90° heat.  Not since 2011 have D.C. residents had a September without any 90° heat, partially a function of how rainy it was.

However, whether or not September is a rainier than average month doesn’t mean it will always be without summer-like heat.  September 2018 is a good example as it finished tied with September 2010 for being D.C.’s sixth warmest on record.  However, the two months couldn’t be more dissimilar from a precipitation perspective.  September 2010 was a largely dry month that finished with above average rainfall (6.02”).  Over 77% of D.C.’s September 2010’s rainfall occurred on September 30 (4.66”) helping illustrate rainfall was an exception rather than the rule during this particular month.  September 2010 also finished with 10 days in the 90s in Washington, D.C.

By comparison, in addition to being the sixth warmest on record, September 2018 was also the fifth wettest.  Three days each had over an inch of rain in the Nation’s Capital.  That’s in addition to the five days highs were in the 90s, illustrating September can be both hot and wet in Washington, D.C.  Sometimes tropical systems impact the Mid-Atlantic Region.  The remnants of former Hurricane Florence brought parts of the D.C. Metro Area record rainfall and severe weather on September 17-18, 2018.  That remains the last time the Nation’s Capital felt any direct impacts from a current or former tropical system during September.

Although September 9 is the latest in the calendar year that triple-digit heat occurred in Washington, D.C., temperatures in the 90s can occur well into October.  While my colleagues and I on the WUSA9 Weather Team expect highs in the 80s to return later next week, no highs in the 90s are expected.  However, it’s too early in the season to rule out the possibility for highs in the 90s.  It just remains a possibility, though increasingly unlikely, through the second week of October.