A Warm and Wet May

May will finish as a significantly warmer and wetter than average month in the Nation’s Capital for a second consecutive year.  With the exception of a few days in the middle of the month, May 2019 has been warmer than average in its entirety.  After a hot stretch of 90s on four out of five days through May 30, today will be a relatively benign weather day with more comfortable temperatures and no severe weather in the DC Metro Area. 

This May’s average temperature (combining daily high and low temperatures) in the Nation’s Capital is 70.8° through May 30.  That’s significantly warmer than NOAA’s 30-year average of 66°, but doesn’t rank among DC’s warmest May’s.  It’s interesting to note, however, that if you include this May, five of DC’s 10 warmest May’s have occurred since 2004, including in 2015 and 2018.

This month has actually been more like May 2018 than May 2015.  That’s because May 2015 was a drier than average month with DC getting less than half its May average.  On the other hand, last May was DC’s sixth wettest on record.  That can largely be attributed to a very warm start to last May, while the second half of May 2018 was very wet with four days that had an inch or more of rainfall.  By comparison, DC’s wettest day this month was May 5 (0.65”).

The warmest temperature this month was 93° on May 29, while DC’s coolest temperature was 50° on May 13 and May 15.  Aside from the three-day period from May 12 – May 14 when high temperatures were in the low 60s (typical of late-March or early-April), May 2019 has been warmer than average.  Although temperatures were in the 90s on four out of the last five days, no record highs were set in the Nation’s Capital.  However, Dulles Airport tied its record high of 90° on May 28.

With yesterday’s rainfall, DC has had 4.97” of rain since May 1.  That’s almost an inch above the monthly average of 3.99”.  Measurable rainfall has occurred on 13 days this month, with the wettest being May 5 (0.65”).  Aside from the warmer and wetter than average conditions this month, the major weather headline in the DC Metro Area has been the frequency of severe weather.  On May 23 and May 30, confirmed tornadoes occurred in Howard County, Maryland.

D.C.’s Warmest May’s (National Airport “DCA” - in Degrees Fahrenheit)

1.  73.2° (2015)
2.  73.0° (1991)
3.  72.4° (2018)
4.  71.8° (2004)
5.  71.6° (1944)
6.  71.4° (2012)
7.  70.5° (1880)
8.  70.1° (1953)
9.  70.0° (1911)
10.  69.8° (1959)

Average: 66.0°

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D.C.’s Wettest May’s on Record (DCA) - Source: NOAA

1.  10.69" (1953, 1889)
3.  10.66" (2008)
4.  10.60" (1886)
5.  8.87" (1948)
6.  8.73" (2018)
7.  8.05" (2009)
8.  7.77" (1989)
9.  7.06" (2003)
10.  6.99" (1946)

Average: 3.99”