Rainfall Trends in the Nation’s Capital

 

A view of Alexandria in the distance from National Harbor, Maryland

January 2023 is well-positioned to finish as D.C.’s fifth drier than average month in the last six, with the exception of December 2022.  Since last August, Washington, D.C. has accrued a rainfall deficit of 4.14” through January 26. 

December 2022 finished with a rainfall surplus of 0.45” in Washington, D.C.  That was largely the result of two exceptionally rainy days that each saw over one inch of rain (December 15, December 22).  Without the combined rainfall total of 3.04” on those two days, last month would have finished with only 0.82” of rain (roughly 25% of D.C.’s December average of 3.42”).  That helps illustrate that with the exception of those two rainy December days, the last six months have been very dry in the Nation’s Capital overall.

Our current drier than average period bears a lot of similarities to another similarly dry period that occurred in late-2017 and early-2018.  Back then, the Nation’s Capital also had five drier than average months in the six-month period of August 2017 – January 2018.  The rainfall deficit in that time swelled to 8.55”, more than double the current rainfall deficit in the Nation’s Capital.  That underscores just how dry those six months were in Washington, D.C.  The only wetter than average month during those six months occurred in August 2017 with a rainfall surplus of 1.33”.

The six-month period in late-2017 and early-2018 was part of a larger 32-month period (August 2015 – March 2018) when all but seven months were drier than average in the Nation’s Capital.  The combined rainfall deficit for that stretch was 16.42”.  As longtime Washingtonians may recall, 2018 went on to become D.C.’s rainiest year on record (66.28”), according to NOAA.  Going from an extended, years-long drier than average period to setting a record for rainiest year represents a major shift in the weather pattern. 

More modest changes are on tap when looking at NOAA’s 8 – 14 day precipitation outlook that covers almost the entire first half of February.  It calls for potentially above average precipitation in the D.C. Metro Area.  February is D.C.’s snowiest month of the year on average.  Washingtonians could see the first accumulating snowfall of the 2022-2023 winter season over the next couple of weeks.