DC’s Seasonal Transition Continues

Freeze Warnings for much of the DC-Baltimore Corridor  (Source: NWS)

Late October and early November is often when the DC Metro Region experiences its first freezing temperatures of the fall season.  Such is the case this fall with the coldest temperatures of the season on tap tonight.  Freeze warnings are in effect for much of the Mid-Atlantic Region tonight and some record lows will be challenged tomorrow morning.

Average low temperatures on November 11 range from 43° at National Airport to 37° at Dulles Airport.  However, today and tomorrow will feel more like January than mid-November, with significantly colder than average temperatures.  Longtime residents may remember that DC’s largest November snowstorm occurred on Veteran’s Day 30 years ago.

Fortunately, no snow is expected this weekend and Washingtonians haven’t had measureable snowfall in November since 1996.  The big story this weekend will be the temperatures.  The last time Washingtonians had temperatures at or below freezing was on March 23, 2017 (30°), while the last time Dulles was that cold was April 9, 2017 (32°).  Tonights below freezing temperatures will put us a few weeks ahead of last year.  The first sub-freezing temperatures at National Airport last fall didn’t occur until November 23, 2016 (32°).  However, Dulles Airport was 30° on October 26, 2016.

There is often several weeks’ difference between when the first subfreezing temperatures occur at National vs. Dulles Airports.  That can be attributed to the local geography as National Airport is located adjacent to the moderating influences of the Potomac River, as well as downtown.  The “urban heat island effect” often keeps urban areas warmer than suburban or rural areas.  Although the Dulles corridor is more developed than 20 to 30 years ago, it’s still significantly more rural than National Airport and away from the Potomac River.  

While weather records for Washington, D.C. date back to 1871, Dulles Airport didn’t open until 1960.  No record lows have been set at National Airport in November since 1976.  However, Dulles Airport has had five record lows in November just since 2003.

November 11 Record Low Temperatures

Washington, D.C. (National Airport – DCA): 26° (1973)
Dulles Airport, Sterling, Virginia: 16° (1973)
Baltimore, MD (BWI Airport): 21° (1973)