Warm and Dry Weather Continues in the Nation's Capital

NOAA's Temperature Outlook through September 22

The warm and dry weather that dominated local weather headlines for long stretches last month has continued into September.  This month has had warmer than average temperatures on six of the first eight days of the month.

NOAA’s temperature outlook through September 22 calls for above average temperatures to continue.  To add to that, high temperatures will reach the low 90s in the DC Metro Area tomorrow and Thursday.  Although not quite at record levels, such temperatures are significantly above DC’s average high temperature of 81° on September 11 and 12.  Average high temperatures in the Nation’s Capital actually fall quite a bit during the month of September from 84° on September 1 to 74° by the end of the month.

That should help illustrate how much warmer than average any 90° heat is for Washingtonians in September.  Dating back to the early 1990s, DC Area residents have averaged nearly four days of 90° September heat, with roughly one day when temperatures climb to between 95° and 99°.  Triple-digit heat has only occurred four times in Washington, D.C. since weather records began in 1871.  The most recent occurrence was on September 2, 1980 with a high temperature of 101°.  DC’s record high of 96° just last Wednesday, September 4 was hottest September temperature in the Nation’s Capital since September 9, 2016 (also 96°).

Contributing to the warm and dry conditions so far this month has been a persistent ridge of high pressure situated off the east coast.  That’s not only acted to pump warm and humid air northward from the Deep South but has also helped suppress widespread showers and thunderstorms.  Longtime Washingtonians might recall that September 2005 was a warm and exceptionally dry month in the Nation’s Capital.  In fact, DC set a new record driest September in 2005 with only 0.11” of rain for the entire month.  September 2005 also had seven days of 90° heat that helped the month finish 4° warmer than average.

However, there was a major shift in the weather pattern by the time October 2005 got underway.  A total of 7.3” of rain occurred in Washington, D.C. on October 7-8, 2005 that contributed to make it the wettest October on record.  That’s similar to how rainy it was in the Nation’s Capital on July 8, 2019 when a daily record 3.44” of rain fell.  A total of only 3.73” of rain has occurred in Washington, D.C. in the two months since then.  That helps underscore how warm and dry it’s been in the Nation’s Capital in recent weeks.  August 2019 had only 1.99” of rain that made it DC’s driest month since March 2018.

Record Highs (Source: National Weather Service)

September 11

Washington, D.C. (National Airport, DCA): 98° (1983)
Dulles Airport (IAD), Sterling, Virginia: 99° (1983)
BWI Airport, Baltimore, Maryland: 100° (1983)

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September 12

DCA: 96° (1931, 1895)
IAD: 95° (1998)
BWI: 96° (1931)