What Explains March Weather in the Nation’s Capital?

 

So far March has continued February’s warmer than average trend in the D.C. Metro Area.  Although four of the last six days have been colder than average, seven of the first eight days of March were quite warm.  March 6 and 7 had May-like highs of 78° and 80°.  Ironically, Saturday’s brief return to winter followed Friday’s April-like high of 63° at National Airport.

There have been a combined 18 record high / record high-low March temperatures in the Nation’s Capital since 1999 according to NOAA.  No record cold has occurred in Washington, DC during March since 1996.  It’s a different story, however, at Dulles Airport in more rural Sterling, Virginia, where a total of 44 record high / record high-low March temperatures have occurred since 1999.  Dulles also had a total of 21 record low / record low-high March temperatures over the same time period.  A record “high-low” temperature means the low temperature on a particular day remained much warmer than average, while a “low-high” temperature is the opposite.

Two primary factors can account for that large difference.  In the Nation’s Capital, where weather records date back to the 1870s, it’s often more difficult to break them.  Meanwhile, weather records at Dulles Airport only date back to the 1960s when it opened.  To add to that, the amount of urbanization in and immediately adjacent to the Nation’s Capital contributes to a more pronounced urban heat island effect compared to the more rural Dulles Airport.

Areas of high pressure that originate over arctic areas of northern Canada and Alaska sometimes build down into the eastern United States during the winter and early spring.  This brings temporary bouts of unusually cold weather to the Mid-Atlantic Region.  However, as these areas of high pressure move off the East Coast, the clockwise wind flow around the high pressure system pumps warmer area from the southeastern United States northward.  That’s often what drives March temperatures to occasionally reach the 60s and 70s in the Nation’s Capital.  

One of D.C.’s warmest March weeks ever had highs in the 80s on five consecutive days through March 16, 1990.  That caused D.C.’s famous Yoshino cherry blossoms along the Tidal Basin to reach their earliest peak bloom on record exactly 32 years ago today.  Meanwhile, the National Park Service announced yesterday that the cherry blossoms reached Stage 3 of 6 on the way to peak bloom.  The “florets extended” stage didn’t occur until March 22 last year, so this spring is well ahead of schedule.

While Washingtonians have experienced 80° March warmth for three consecutive years now, there hasn’t been any shortage of cold and snowy weather during March in recent years.  In addition to this past Saturday’s snowfall, Washington, D.C. had measurable snowfall in seven consecutive March’s (2013 – 2019), the longest such streak on record.  Fortunately, for those tired of the cold and snow, NOAA expects above average temperatures to continue for much of the upcoming week and into next week.  That will only accelerate D.C.’s cherry blossoms to reach another earlier than average (April 4) peak bloom.