D.C.’s Rainy and Cool Start to May

 

Mostly Sunny & Stellar Weather in Potomac, Maryland

The first eight days of May 2022 have been unusually rainy and cool in the Nation’s Capital.  It rained on six of the first eight days of May with a total of 3.30”.  Washington, D.C. averages 3.94” of rain during the entire month so D.C. residents have already had over 80% of May’s average rainfall.  The last two May’s have been drier than average in the Nation’s Capital so this month is already well-positioned to end that streak.

The wettest days of the month were May 6-7 with a 2-day rainfall total of 2.29” at National Airport.  It was also the first time since 2018 Washington, D.C. had at least two May days of 1.00”/+ of rain.  That’s not to say this month will end up being as rainy was May 2018 was with 8.73”, but this month has simply gotten off to a very wet start.

Temperatures were cooler than average on four of the first eight days of the month.  While today’s temperatures will be milder than yesterday, they will still be cooler than average in the Nation’s Capital.  May has already been 4.0° cooler than average in Washington, D.C. as of May 8.  In a relatively rare feat, the Nation’s Capital had highs in the 50s on May 7 and May 8.  Although D.C. also had consecutive highs in the 50s on May 29-30, 2021; it remains relatively unusual as the Nation’s Capital has averaged just one May day with highs in the 50s over the last 30 years. 

Washington, D.C. has had as many as five May days with highs in the 50s in May 2016, but 13 May’s since 1997 haven’t had any days with highs in the 50s.  By comparison, the Nation’s Capital has averaged close to two May days with highs in the 90s since the early 1990s, almost double the average number of days with highs in the 50s.  D.C. Area residents can expect 95°/+ May heat roughly once every five years.

Having a rainier than average May, as this month has been so far, doesn’t necessarily mean it will be a cooler than average month.  May 2020 and May 2021 were each cooler than average in the Nation’s Capital, but were also drier than average.  May 2018 and May 2019, for example, were each wetter than average and also rank among D.C.’s Top 10 warmest on record.

Unlike this month that’s gotten off to a cool and wet start, May 2018 got off to a hot and dry start.  No measurable rainfall occurred during the first 11 days of May 2018, when 10 days were also warmer than average.  That was followed by measurable rainfall on eight consecutive days from May 12 – May 19.  This month couldn’t have gotten off to a more different start than May 2018, but it doesn’t mean by any stretch that D.C. couldn’t see a warmer than average month this May.

NOAA’s Climate Prediction Center expects above average temperatures to envelop the D.C. Metro Area as the week wears on, but temperatures could be cooler than average again later in the month.  However, average daily temperatures continue to rise as May wears on.  That means while D.C. residents could enjoy highs in the low to mid 70s during the second half of May, that would still be cooler than average.  That’s because daily average high temperatures in the Nation’s Capital reach the upper 70s (78°) starting on May 21.