Saturday’s Rainfall Produces More Records

The combination of Saturday afternoon’s heavy rain and below average temperatures made for a miserable weather day for the DC Metro Area.  It also resulted in a slew of weather records and inched 2018 closer toward setting a new record for wettest year overall.  The 1.42” of rain yesterday at National Airport was the 22^nd day of 2018 that at least an inch of rain fell.  That broke the previous record of 21 such days from 1878.

A total of 7.11” of rain has occurred in Washington, D.C. so far this month putting November 2018 only 0.07” behind the 1877 record for DC’s wettest November (7.18”).  By comparison, the Nation’s Capital averages only 3.17” of rain in November, so we’ve more than doubled that total with the potential to break the monthly record tomorrow.  Our eight previous Novembers (2010 – 2017) all happened to be drier than average.

Meanwhile, Dulles Airport has had 7.45” of rain so far this month and that’s good for second wettest November behind only 1963 (7.83”).  Overall, Dulles Airport has had 60.75” of rain since January 1, making 2018 its second wettest year on record behind only 2003 (65.69”).  BWI Airport has had 7.72” of rain so far this month and that’s already made this month Baltimore’s wettest November on record, according to the National Weather Service.  BWI Airport – Baltimore’s official weather reporting site – also set a new record for highest annual rainfall total.  Since January 1, BWI has had 64.86” of rain, eclipsing the previous record of 62.66” of rain from 2003.

With the rest of November and the entire month of December remaining, there’s a strong likelihood that Washington, D.C. and Dulles Airports will join BWI Airport with 2018 becoming their wettest years on record.  DC is only 1.33” of rain away from reaching that benchmark.  NOAA recently issued its monthly outlook for December and it calls for near average precipitation in the Mid-Atlantic Region.  Since Washingtonians average 3.05” of rain in December, that would be more than enough to make 2018 DC’s wettest year on record.

It’s remarkable that Washington, D.C. is even having this conversation for wettest year on record considering the dry 31-month period from August 2015 through March 2018.  During that time, all but seven months were drier than average and that produced a total rainfall deficit of 16.42”.  By comparison, the six-month period from April 1 through October 31 produced a rainfall surplus of 20.63” – more than eliminating the accrued rainfall deficit from the previous 31 months.

Washington, D.C.’s Five Wettest Novembers (Source: NOAA)

1.  7.18”  (1877)
2.  6.70”  (1963)
3.  6.43”  (1932)
4.  6.33”  (1952)
5.  6.05”  (1972)

Average: 3.17”

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Washington, D.C.’s Five Wettest Years (Source: NOAA)

1.  61.33” (1889)

2.  60.83” (2003)

3.  60.09” (1878)

4.  58.17” (1886)

5.  57.54” (1948)

Average: 39.74”