Extreme May Temperatures

This weekend has featured some of DC’s coldest May weather in more than a decade.  Record low-high temperatures were set yesterday at all three DC Area airports.  The May 9 high temperature of 52° at National Airport tied the record low-high for the date, originally set in 1877.  One has to go back to May 1, 1963 (51°) for the last time Washingtonians had a May high temperature colder than yesterday’s.  Making matters worse, yesterday’s gusty northwest winds created wind chills in the 30s and 40s.

Low temperatures both yesterday (37°) and today (38°) fell into the 30s across the DC Metro Area.  That’s rare in the Nation’s Capital, especially on consecutive days.  Although not record-setting, both temperatures were much colder than DC’s average lows in the mid-50s during the second week of May.  The last time Washingtonians felt the 30s in May was 2005.

Weather records only date back to 1960 at Dulles Airport so there’s a much smaller pool of weather records.  The conditions are quite different between National and Dulles Airports.  There is a significant urban heat island effect at National, which also feels the influence of the Potomac River.  Conditions are more rural around the landlocked Dulles Airport and that helps create an ideal setup for radiational cooling.  Consequently, Dulles was colder both yesterday (33°) and today (33°).  Although not record-setting, that was much colder than average lows of 49° for May 9 and 10.  

In addition to National Airport, record low-high temperatures were also set at Dulles and BWI Airports yesterday.  Fortunately for those tired of the chilly and rainy conditions, temperatures today have been considerably warmer with highs in the 60s.  Temperatures will reach the 80s by the end of the upcoming work week.

Prior to this week, the last time DC residents experienced a daily high temperature in the 50s was on May 12, 2017 (59°).  There was a pivot to above average temperatures after that, with a high of 91° on May 17, 2017.  Although no temperatures that warm are on the horizon this week, Washingtonians would welcome even average temperatures in the 70s.  All but eight days have been cooler than average in the Nation’s Capital since April 10.  Residents of the DC Metro Area know to enjoy these cool temperatures, since the hazy, hot and humid conditions so common during the summer will be here soon.