D.C.’s Warm and Dry Start to December

 

The first third of December has been unusually warm in the Nation’s Capital, with five days considerably warmer than average.  There were three days with highs in the 60s at National Airport – D.C.’s official weather reporting site – along with one day in the 70s.  When D.C.’s high temperature reached 70° on December 6, it became the first December day in the Nation’s Capital with highs of at least 70° in six years.

D.C. warmest December on record came in 2015, which had three days with highs in the 70s.  There were also 11 days high temperatures were in the 60s.  Although this month isn’t expected to challenge for D.C.’s warmest, it is well-positioned to finish as a warmer than average December for the tenth time in the last 11 years.  In fact, December has been so warm over the last decade that D.C.’s average monthly temperature (combining daily high/low temperatures) has risen considerably.

December’s average temperature in the Nation’s Capital for the 30-year period of 1981-2010 was 39.7°.  However, since NOAA updated its climate data last winter to reflect the 30-year period of 1991-2020, D.C.’s average December temperature has risen 2.0° to 41.7°.  That’s a huge difference in average monthly temperature over a relatively short period of time.  NOAA’s Climate Prediction Center expects the warmer than average weather to continue for the next one to two weeks.

If high temperatures today reach 70°/+ at National Airport, then that would be the second time this month.  While no 70° December warmth occurred in the Nation’s Capital before this week since 2015, it happened in four consecutive years through 2015.   That was really unusual, though, that one had to go back to 1998 to get four Decembers with 70° warmth in the Nation’s Capital prior to 2011. 

It has also been a dry month, with only 0.01” of rain through December 10.  There has been a near 50/50 split of wetter vs. drier than average Decembers over the last decade, with six that were wetter than average.  NOAA also expects near to slightly above rainfall the rest of the month.  However, given how dry it’s been so far this month, it would take above average rainfall the rest of the month for the Nation’s Capital to merely finish with an average amount. 

Washington, 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)