Final Month of 2020 Gets Underway

 

Last month featured some very memorable weather in the DC’s Metro Area with the first warmer and wetter than average November since 2009.  November’s average monthly temperature (combining daily high and low temperatures) of 54.3° tied November 2020 with 1985 as DC’s fourth warmest on record.  It was also a rainy November in the Nation’s Capital with a monthly total of 6.14”.  That made last month DC’s sixth wettest on record. 

What kind of weather can Washingtonians expect now that December is underway?  Daily average high/low temperatures range from 52°/37° on December 1 to 44°/29° on December 31.  There has been a large range in temperatures, historically, during the month of December in the Nation’s Capital.  DC’s all-time highest December temperature is 79° on December 7, 1998.  Meanwhile, DC’s coldest December temperature is -13° on December 31, 1880.  Weather records in Washington, D.C. date back to 1871. 

There have been some interesting temperatures trends in the Nation’s Capital during the month of December over the last two decades.  The fact that 13 of the last 20 December’s have been warmer than average hides how streaky December’s temperatures were in that time.  DC had an even 50/50 split of warmer and colder than average December’s between 2000 and 2009.  However, eight of 10 December’s between 2010 and 2019 were warmer than average, including DC’s warmest on record in 2015.

Washington, D.C. averages 3.17” of December rainfall.  The Nation’s Capital also averages 2.3” of December snowfall.  Since 2000, there have been 12 December’s with measurable snowfall and five with a trace of snow.  A “trace” of rain or snow is not enough to measure.  There have been only three Decembers in the last 20 years without any snowfall, most recently in 2018. 

However, a warmer than average month, as DC residents experienced last month, isn’t a good indicator of what the weather will be like the following month.  For example, November 2009 was warmer and wetter than average in the Nation’s Capital, but was followed by DC’s snowiest December on record.  NOAA expects December to be warmer and wetter than average in the Nation’s Capital.

Some DC residents may correctly assume that 2020 has been a rainier than average year.  That’s true, as 52.40” of rain fell through December 1, 2020 – or 15.6” above average.  The Nation’s Capital needs only another 0.19” of rain for 2020 to become one of DC’s 10 wettest years overall.  If DC were to get only average rainfall this month, then 2020 would become DC’s 7^th wettest year on record.