Hot and Dry

This month is on the verge of finishing among the Top 5 hottest and driest September’s on record in the Nation’s Capital.  That shouldn’t surprise area residents considering how hot and dry the months of July and August were.  Although the seasons changed and it’s officially autumn, this month has remained very summer-like. 

Washington, D.C. has had some of the hottest September weather in decades this year.  There have been seven days at or above 90 degrees, including four days that were at least 95 degrees.  That includes a streak earlier this month of three consecutive days of 95-degree heat.  The last time Washingtonians experienced such hot September weather on consecutive days was in 1985. 

Area residents also endured the hottest September day since 2010, when it was 98 degrees on the 8^th.  Also, today is the 6^th anniversary of when the high temperature reached 99 degrees at National Airport.  That was DC’s hottest September temperature since September 2, 1980 (101 degrees).  Just yesterday, Washington, D.C’s high temperature reached 90 degrees.  Although that wasn’t a record high for the date, the average high for September 23 is just 77 degrees.

Through September 23, Washington, D.C.’s average monthly temperature (combining daily high and low temperatures) is 78.4 degrees, according to the National Weather Service.  Although that average will come down a bit during the final week of the month with more seasonal temperatures on tap, it won’t fall enough to keep this month from finishing among the warmest Septembers on record. 

Many Washingtonians have likely noticed, too, just how dry the last few months have been in the Mid-Atlantic Region.  September has a rainfall deficit of 2.3” at National Airport, while the yearly deficit is 3.77”.  The combination of below average rainfall and hot weather – 53 days of 90 degree heat since Independence Day (58 for the year) – have led to abnormally dry conditions for parts of the DC Metro Region on the Drought Monitor Index. 

The relatively recent hot and dry summers of 1999 and 2011 in the Nation’s Capital also featured significant rainfall deficits.  They came to an abrupt end with the arrival of decaying tropical systems.  However, there aren’t any tropical systems on the horizon that might bring the area any relief from the continuing dry weather.  My colleagues and I on the WUSA9 weather team are tracking the potential for a few showers late Monday into Tuesday, but no significant rainfall is expected the rest of the month.

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Driest Septembers on Record (DCA)

1.  0.11” (2005)

2.  0.14” (1884)

3.  0.2” (1967)

4.  0.32” (1977)

5.  0.51” (2016 – through 9/23)

6.  0.53” (1941)

7.  0.6” (2007, 1986, 1906)

10.  0.63” (1954)

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Warmest Septembers on Record in Washington, D.C. (Combining Daily Highs and Lows)

1.  78.2 (1881)
2.  77.1 (1980)
3.  76.0 (1930)
4.  75.5 (2010)
5.  75.4 (1998)