Has May Been Warmer than Average?

Spring is a Beautiful time of year !

Many Washingtonians have been thrilled with the summer like warmth so far this month.  It has been at least 80 degrees in the Nation’s Capital every day since May 3.  In fact, today could be this year’s first day of 90 degree heat at National Airport.  The last time it was at least 90 degrees in Washington, D.C. was on September 11, 2014, when it was 91 degrees.  However, today’s record high of 93 degrees downtown should be safe, although, the record high of 89 degrees could be approached at Dulles Airport.

Yesterday’s high was 83, which is typical for June 11.  During the month of May, the warmest average high temperature in the Nation’s Capital is 80 degrees on May 31.  So to start the month with a string of ten days in the 80s is fairly remarkable.  High temperatures tomorrow will be much more seasonal in the mid-70s.  Although ten days with temperatures of at least 80 degrees is unusual in May in this part of the country, it isn’t unprecedented.

Three years ago, May was significantly warmer than average and included a nine day stretch with high temperatures of at least 80 degrees that began May 22.  May 2012 finished more than 5 degrees warmer than average and was a harbinger of what followed in June and July.  June 2012 saw the hottest June temperature on record in the Nation’s Capital (104 degrees on the June 29).  July 2012 set a new record for most days of triple digit heat (7) in a month including four consecutive 100 degree days in Washington, D.C.  May 2011 saw a similar ten day stretch of weather with highs of least 80 degrees before July 2011 became the hottest July on record at National Airport.

May has also been cooler and wetter than average in the not too distant past.  May 2005 featured only three days with high temperatures in the 80s and four days where high temperatures remained in the 50s (typical of March).  According to the National Weather Service, May 2003 had 23 days of rain that helped suppress temperatures.  It remains the coolest May in Washington, D.C. since 1967.  By comparison, this month is currently more than eight degrees warmer than average.  Although all but one day this month has featured warmer than average temperatures, this month’s streak of days in the 80s isn’t officially a heat wave.  A “heat wave” is defined as a minimum of three consecutive days of 90 degrees or greater.  The last “heat wave” to occur in the Nation’s Capital during the month of May came in 2013 (May 29-31).

There is no official correlation between a warmer than average May and what the weather will be like during the summer in the Nation’s Capital.  The summer-like pattern that’s been in place so far this month could remain in place giving Washingtonians a warmer than average summer as was the case in 2011 and 2012.  The weather pattern could also shift dramatically and become cooler and wetter than average as May 2003 and May 2005 were.  My colleagues and I on the WUSA 9 weather team will keep readers apprised of the latest forecasts for the rest of the spring and summer.