DC’s Record March Rainfall

 

DC’s March 24 rainfall total of 1.69” was not only a daily record, but was also DC’s rainiest day so far in 2021.  It also eliminated any chance March 2021 had for finishing among DC’s driest.  Prior to yesterday, a rainfall total of only 0.66” had occurred since March 1.

The record rainfall yesterday was not only DC’s wettest day since November 30, 2020 when 2.39” fell, but also DC’s wettest March day since March 21, 2019 (1.96”).  While not common, such heavy rain does occur periodically in the DC Metro Area during this time of the year.  DC’s wettest March day on record occurred on March 9, 1881 (2.79”).

Unlike February 2021 that had 15 days with measurable rainfall, DC had three days with measurable rainfall so far this month.  DC’s record rainfall yesterday was double the heaviest daily rainfall to occur during all of last month (0.84” on February 28).  Despite yesterday’s rainfall, this month has an ongoing rainfall deficit of 0.27”.  That’s the result of DC’s longest dry stretch in 18-months, which recently ended.

The 16 days without measurable precipitation in the Nation’s Capital between March 2 and March 17 was the longest since a 17-day stretch in September 2019.  That month finished as one of DC’s driest Septembers on record.  However, with several more rain chances before the end of the month, March 2021 should finish as a wetter than average month.  Additional rainfall is good news for allergy sufferers hoping for a respite from the rising levels of tree pollen.

If March 2021 finishes wetter than average month, then it would be a relatively rare occurrence.  Four of the last five March’s, through 2020, were drier than average in Washington, D.C.  However, that had little bearing on total rainfall in 2018 and 2020 because they finished as DC’s wettest and seventh wettest years on record, respectively.  According to NOAA’s 30-year average from 1981-2010, the Nation’s Capital has averaged 3.48” of March rainfall.  NOAA will release updated climate data later this spring, which will be for the 30-year period from 1991-2020.

DC’s Ten Wettest March’s (Source: NOAA)

1.  8.84” (1891)
2.  8.45” (1994)
3.  7.43” (1953)
4.  7.24” (1884)
5.  6.82” (1993)
6.  6.61” (1881)
7.  6.45” (1932)
8.  6.41” (1886)
9.  6.17” (1924)
10.  6.14” (1984, 1912)

DC’s Ten Driest March’s (Source: NOAA)

1.  0.05” (2006)
2.  0.57” (1910)
3.  0.74” (1986)
4.  0.84” (1945)
5.  0.98” (1894)
6.  1.02” (2012, 1947)
8.  1.07” (1915)
9.  1.16” (2016)
10.  1.27” (1927)