May's Warm Start

NOAA expects May 2018 to be a warm month

While March and April finished cooler than average in Washington, D.C., May has gotten off to a very different start.  It’s been warmer than average on 10 of the first 11 days of the month.  Above average temperatures are expected to continue next week, putting the Nation’s Capital in a good position to have its warmest May since 2015.

May has featured some very unique weather in the Nation’s Capital in recent decades.  While 10 of the 15 May’s from 1992 through 2006 were cooler than average, 10 of those 15 summers were warmer than average.  By comparison, eight of the 11 May’s from 2007 through 2017 were warmer than average in D.C.  

There is no strong relationship, however, between May temperatures in the D.C. Metro Area and what the upcoming summer will be like.  May 1997 is a good example of that fact.  It had cooler than average temperatures on 17 out of the 31 days and subsequently finished 3.1° cooler than average, according to the National Weather Service.  But, the summer of 1997 proceeded to finish only 0.7° cooler than average in Washington, D.C.  That’s despite having five days of triple-digit heat between June 1 and August 31.  By comparison, May 2000 was 1.8° warmer than average, while the summer of 2000 was D.C.’s coolest since 1972.

National Weather Service data also shows May is D.C.’s wettest month of the year with an average of 3.99” of rain.  Sometimes a lot of rainy days can lead to cooler than average month.  Such was the case in May 2003, when D.C. had measurable rainfall on 20 out of 31 days with a monthly total of 7.06”.  That ranks as D.C.’s eighth wettest May and also contributed to making it 4.3° cooler than average.  In fact, May 2003 was D.C.’s coolest since 1967.

More recently, May 2016 was another cooler than average month in the Nation’s Capital with measurable rain on 19 days.  However, D.C. residents may recall that summer was one of the hottest on record with the first 100° heat since 2012.  That helps illustrate again, that while the dominant weather pattern in May can sometimes continue into the summer months, May’s weather does not accurately portend what will occur in the summer.  NOAA expects this month to be warmer than average in the Nation’s Capital with near average precipitation.  Meanwhile, their seasonal outlook for the summer is for warmer and wetter than average conditions in the Mid-Atlantic Region.