From Record Dry Weather to Record Rainfall

Three-Day Rainfall Estimates (Source: NOAA)

The deluge that began Saturday, July 21 has continued and has put the Nation’s Capital in the unique position of being able to surpass the 1945 record for wettest July (11.06”) on record.  That would be remarkable considering Washington, D.C. set a record for driest start to July with no measurable rainfall from July 1 through July 16.

July 21 was the wettest day across the DC Metro Area in recent memory.  The 4” of rain that occurred Saturday came just four days after 2.79” fell on July 17.  According to the National Weather Service (NWS), that was the first time that Washington, D.C. has had two July days with at least 2.79” of rain.  As of July 30, 9.70” of rain has occurred at National Airport and that makes it the fourth wettest on record.  Some Washingtonians may recall that July 2017 was the eighth wettest on record with 9.15” of rain. 

While weather records in the Nation’s Capital date back to 1871, weather measurements have been made at National Airport (DCA) since it opened in 1941.  Looking exclusively at DCA records, July 2018 has already become DC’s fourth wettest on record.  The last time eight or more inches of rain fell in July in consecutive years in Washington, D.C. was in 1969-1970.

The last time the Nation’s Capital had two months in a calendar year with eight or more inches of rain was in August-September 2011.  Unlike that rainy two-month period, when a high volume of the rain was attributable to tropical systems (Hurricane Irene and the remnants of Tropical Storm Lee), the exceptionally wet months of May 2018 and July 2018 have not been the direct result of any tropical systems.  July 2018 is also the fourth consecutive wetter than average month in the Nation’s Capital.  The last time four or more consecutive wetter than average months occurred here was a seven-month stretch from February 2014 – August 2014.

Below are some important records and benchmarks from the NWS.  NOAA expects the wet weather pattern of the second half of July to continue into early August in the Mid-Atlantic Region.

Washington, D.C.’s Wettest July's

1.  11.06” (1945)

2.  10.63” (1886)

3.  9.95” (1905)
4.  9.70” (2018) as of July 30

5.  9.59” (1922)

6.  9.44” (1969)

7.  9.41” (1917)
8.  9.15” (2017)

9.  8.40” (1891)

10.  8.37” (1878)

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Washington, D.C.’s Twenty Wettest Months Overall

1.  17.45” (September 1934)
2.  14.41” (August 1928)
3.  14.36” (August 1906)
4.  14.02” (June 2006)
5.  12.93” (August 1875)
6.  12.36” (September 1975)
7.  11.94” (June 2015)
8.  11.53” (June 1972)
9.  11.06” (July 1945)
10.  10.94” (June 1900)
11.  10.81” (September 1876)
12.  10.69” (May 1953)
12.  10.69” (May 1889)
14.  10.66” (May 2008)
15.  10.63” (July 1886)
16.  10.60” (May 1886)
17.  10.27” (September 1999)
18.  9.97” (June 2013)
19.  9.95” (July 1905)
20.  9.91” (August 1933)