A Peaceful Close to an Unsettling Year

 

One of the final sunsets of 2020

December 2020 has kept with the overall pattern of 2020 being warmer and wetter than average in the Nation’s Capital.  DC’s average monthly temperature (combining daily high/low temperatures) is 1.4° above average through December 30.  There has been 4.96” of rain so far this month, making it DC’s ninth wetter than average December of the last 10 years.

A few showers are possible this afternoon, but won’t add up to the 0.2” of rain that DC needs to tie 1948 for sixth wettest year.  A total of 57.34” of rain has occurred at Reagan National Airport since January 1.  Oddly enough, four of the first six months of 2020 were drier than average in the Nation’s Capital.  However, there have been three days just this month with an inch of more of rain.  That’s compared to only two such days in December 2018, which capped off DC’s rainiest year on record. 

Washingtonians may wonder what typical New Year’s Eve weather is like.  Based on NOAA’s 30-year average from 1981-2010, DC’s “average” December 31 high/low temperatures are 44°/29°.  Dulles Airport is a touch colder with averages of 43°/24°.  There has been some very mild December 31 weather in the DC Metro Area such as in 2011 with a high/low of 62°/46° or 2015 (57°/44°).  There have also been frigid conditions in the Nation’s Capital on New Year’s Eve such as in 2017 with a high/low of only 23°/16°.

Measurable rainfall has only occurred five times in the last 20 years on New Year’s Eve in Washington, D.C. with the last being 2018.  Official weather measurements for the Nation’s Capital are kept at National Airport.  Dulles Airport in nearby Sterling, Virginia has had some even colder New Year’s Eve weather.  The high/low temperature at Dulles on December 31, 2017 was 21°/10°, compared to the balmy 2004 high/low of 60°/40°.  DC’s weather last New Year’s Eve featured an above average high/low of 54°/43° and dry conditions.

NOAA is getting ready to update the time period used for measuring “average” weather in the United States.  Starting next month, the 30-year time period will shift to 1991-2020.  Meteorologists will be able to see a discernable difference once that change is made.  Daily low temperatures, in particular, should be warmer in the Nation’s Capital and other urban/suburban areas.