December 2021: Unusually Warm and Dry in the Nation’s Capital !

 

December 2021 has been a memorable weather month and will finish as one of D.C.'s warmest and driest on record.  It will also be the first December to be both warmer and drier than average since 2012.  There’s been ample opportunity for outdoor activities such as dining al fresco or hiking, with or without your dog.

This month's average temperature (combining daily high/low temperatures) is 47.2° through December 29, more than 5° above average.  There were 10 days this month with high temperatures of at least 60° (including two days in the 70s).  D.C.'s high temperatures of 70° on December 6 and 11 gave Washingtonians their first taste of 70° December warmth since 2015.  This month has had more days with high temperatures in the 60s (eight) than lows at or below freezing (six) and will finish as D.C.’s second warmest behind only 2015.

It has also been a very dry month with only 0.45" of rain as of December 29.  While there have been a lot of cloudy and damp days, very little rain has fallen with measurable rainfall on only six days.  That's in addition to seven days with a "trace" of rain, or too little to measure.  December will finish without any accumulating snowfall in the Nation’s Capital for the sixth time in the last eight years.  

December's dry weather continues the dominant weather trend in the Nation's Capital during the final three months of 2021.  D.C. has accrued a rainfall deficit of 5.11" since October 1.  That has led to "abnormally dry" conditions for much of the D.C. Metro Area, with moderate drought conditions for much of central and southern Virginia based on the most recent Drought Monitor Index.  Despite the dry autumn, 2021 will still finish with a modest rainfall surplus of more than 2".  That's largely due to how rainy August was with 9.07", nearly triple D.C.'s August average of 3.25".

Some may wonder what a warm and dry December means for the rest of the winter.   Warmer and drier than average weather over a month isn't a reliable indicator of what an entire season will be like.   For example, December 2015 was D.C.’s warmest on record.  However, the epic January 2016 blizzard occurred a few weeks later.  The right ingredients only need to come together once to produce appreciable snowfall.

D.C.’s Driest December’s  (Source: NOAA)

1.  0.19” (1889)
2.  0.22” (1953)
3.  0.30” (1898)
4.  0.47” (1965)
5.  0.50” (2017)
6.  0.65” (1980)
7.  0.71” (1937)
8.  0.85” (1979)
9.  0.97” (1873)
10.  1.07” (1925)

D.C.’s Warmest December’s (Source: NOAA)

1.  51.2° (2015)
2.  45.6° (1984, 1889)
4.  45.5° (2001, 1982, 1971)
7.  45.4° (2012)
8.  45.0° (2011, 1923)
10.  44.5° (1990)