September 2019 Has Been Exceptionally Warm and Dry

The unusually dry conditions that have dominated local weather headlines over the last two months will continue for the next few days.  That will help September 2019 finish was one of DC’s driest on record.  High temperatures reached the low to mid 90s in the DC Metro Area for the sixth time this month on September 23.

DC’s average September temperature (combining daily high and low temperatures) is significantly warmer than average at 76.8° through September 24.  All but five days so far this month have been warmer than average.  Record high temperatures were set at National Airport on September 4 and September 12.  A record high temperature was tied on September 12 at Dulles Airport and a new one was also set on September 23.

In addition to being a warm month, September has also been exceptionally dry.  That’s a far cry to last September that finished as DC’s fifth wettest on record with 9.73”.  By comparison, a paltry 0.11” of rain has occurred so far this month.  That would tie 2005 for DC’s driest on record if no more rain occurs.  Making this month’s dry weather even more remarkable is how 14 of the last 17 months have been wetter than average in the Nation’s Capital dating back to April 2018.

Making September’s dry weather even more troublesome for area gardens and allergy sufferers is that August 2019 was also quite dry in the Nation’s Capital.  Washingtonians haven’t experienced consecutive drier than average months since September 2017 – January 2018.  It wouldn’t take much, however, for the DC Metro Area to make up the rainfall deficit of 3.77” that’s developed since August 1.  It would only take one decaying tropical system to bring the Mid-Atlantic Region a few inches of rain.  For example, Washington, D.C. saw a two-day rainfall total of 4.69” from the remnants of Hurricane Sandy in October 2012.

Unfortunately, NOAA’s extended outlook is for continued warmer and drier than average weather conditions for much of the eastern United States from October 2 through October 8.  That’s not good for area gardeners and fall foliage enthusiasts.  Prolonged stretches of warmer and drier than average weather in the late-summer and early-fall can cause the leaves to dry out prematurely.  That diminishes the amount of colors that are possible during peak leaf viewing season.

DC’s Warmest September’s Based on Average Monthly Temperature (Source: National Weather Service - NWS)

1.  78.2° (1881)
2.  77.1° (1980)
3.  76.0° (2016, 1930)
5.  75.5° (2018, 2010)
6.  75.4° (1998)
8.  75.0° (2005, 1970)
10.  74.9° (2015)

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DC’s Driest September’s (Source: NWS)

1.  0.11” (2005)
2.  0.14” (1884)
3.  0.20” (1967)
4.  0.32” (1977)
5.  0.53” (1953)
6.  0.60” (2007, 1986, 1906)
9.  0.63” (1954)
10.  0.65” (1955)