As people celebrate the unofficial
start to summer this Memorial Day weekend it’s a good time to reflect upon some
of unique weather that’s occurred across the Mid-Atlantic Region this month. It has been DC’s first wetter than average
month since last May with 5.25” at National Airport through May 26. There have been 15 days with rain this month
that’s also had an effect on temperatures.
Given the frequent
rainfall and cloud-cover, this month could become DC’s
first cooler than average month since May 2016. Average temperatures this month are 0.6° cooler
than average through May 26. The same
weather pattern that has brought such frequent rainfall has also helped keep
temperatures near or slightly below average.
Given the early start to this year’s allergy season in the DC Metro
Area, not everyone is disappointed by this month’s cooler and wetter than
average conditions.
Although this month has
featured more rain than any month in a year, May 2017 is still short of how wet
last May was in the Nation’s Capital.
May 2016 saw 5.65” of rain at National Airport and was also 2.1° cooler
than average. According to the National
Weather Service, there was a total of 22 days of rain last May in the Nation’s
Capital (that includes a streak of 15 consecutive days with measurable rainfall
from April 27 – May 11, 2016).
While last May had a
higher overall number of rainy days, this May has had more days with heavier
rainfall with four days of at least 0.5” of rain compared to three such days a
year ago. This month’s rainfall has helped eliminate the
drought conditions that had developed across much of the Mid-Atlantic Region.
Despite the predominantly
cloudy and damp conditions this month, there have already been two days of 90°
heat so far this month and three so far this year. The first 90° day of 2016 didn’t occur until
June 11. Also, last May had five days
where high temperatures remained in the 50s (more characteristic of March),
this month has had only one such day.
While such temperatures
are unusually cool for May in Washington, D.C., no record lows have been set at
National Airport. The last time
Washingtonians experienced record lows during the month of May was in 2002,
when the temperature fell to 42° on May 20.
Meanwhile, Dulles Airport, where the data pool is considerably less than
downtown, several record low temperatures were set last May. Dulles Airport has also had 6.61” of rain so
far this month making this its wettest month since June 2015 (7.44”). There are several more rain chances across
the Mid-Atlantic Region during the Memorial Day weekend.
I guess May's rain has alleviated some of the arid conditions outlined in your last post.
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