Feeling More Like Summer

 

As the final month of meteorological spring, May often features some very diverse weather in the Nation’s Capital.  Unlike March or April that can still have chilly temperatures, summer-like heat become more common during May.  Temperatures continue to rise throughout the month as both the amount and intensity of the daily sunlight increases with the rising sun angle.

Temperatures in the Nation’s Capital range from an average high/low of 71°/52° on May 1 to 80°/61° on May 31.  DC’s hottest May temperature on record is 99° that occurred on May 31, 1991.  By comparison, the coldest May temperature was 33° on May 11, 1906.  Seven of the last 10 May’s through 2020 were warmer than average, while seven of the 10 from 2001 – 2010 were cooler than average. 

With a monthly average temperature of 63.8°, last May was DC’s coolest since 2005.  However, four of DC’s 10 warmest May’s have occurred in just the last decade.  There have been exceptions as May 2016 finished more than 2° cooler than average and had five days with March-like highs in the 50s.  Conversely, May 2018 got off to a hot start with highs in the 90s on May 2 – May 4, but finished as DC’s third warmest May. 

May has the highest average monthly rainfall in the Nation’s Capital with 3.99” for the 30-year period of 1981 – 2010.  Like with temperatures, there has been a near 50/50 split with 11 of the last 20 May’s being drier than average.  However, there have been exceptions as four of DC’s 10 wettest May’s occurred in the last 20 years. 

May is an active severe weather month in the DC Metro Area.  Looking at DC’s May climate records, one can see that on several dates a trace (enough to accumulate, but not enough to measure) of snowfall has occurred.  That wasn’t actually snow, but hail.  For example, on May 2, 2016 a severe weather outbreak produced a lot of hail in the DC Metro Area.  Small accumulations of hail were reported in spots such as at National Airport where a “trace” of frozen precipitation was observed.