July 2017 (9.15”) and July 2018 didn’t see any rain
from tropical systems. However, both
months featured slow-moving thunderstorms that produced heavy rainfall. Earlier this month, a rare July Nor’easter
also brought record rainfall. More than
a third of last July’s rainfall occurred on a single day (July 28, 2017: 3.31”)
and more than half of this month’s rainfall occurred on just two days (July 17:
2.79”, July 21: 4.00”). According to the
National Weather Service, Washington, D.C. averages 3.73” of rain in July.
June 2006 was the wettest June on record in
Washington, D.C. with a monthly total of 14.02”. None of that rainfall was caused by a tropical
system. Almost 75% of that total
(10.34”) occurred in just three days (June 25-27). A stagnant weather pattern that resulted from
a stalled jet stream over the Appalachian Mountain chain, combined with a
steady feed of moisture from the Atlantic Ocean, led to DC’s record June 2006
rainfall.
June 2015 was similar in that no tropical systems
influenced the Nation’s Capital, but three days still saw record daily rainfall
totals of more than 2”. That contributed
to making June 2015 DC’s second wettest June (11.94”). May 2008 was also a wetter than average month
with a total of 10.66” at National Airport.
That was largely the result of severe weather and an unusual May Nor’easter.
On the other hand, tropical systems contributed to
making September 1999, August 2011 and September 2011 significantly wetter than
average in the DC Metro Area. Weakening
Hurricane Floyd brought DC 3.67” of rain on September 16, 1999. That was after the remnants of Hurricane
Dennis produced heavy rainfall earlier in the month. The Mid-Atlantic Region also saw
record-setting rainfall in August-September 2011 due to Hurricane Irene’s
landfall in North Carolina and the remnants of Tropical Storm Lee.
There is a chance Washington, D.C. could add to this
month’s total of 9.19” of rain. In any
event, July 2018’s place in weather history is secure.
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