December is the darkest and second coldest month of the year and is a time when seasonal snowfall totals begin to rapidly accumulate, but buried deep within the winter chill and darkness, signs of Spring already begin to appear. The all time record coldest temperature was recorded in Kansas City back in 1989 when the overnight low fell to -23. That same cold outbreak brought lows to -16 in St. Louis. Recent years have been much kinder with no lowest temperature zero or below (since 2008) in St. Louis. Kansas City dropped to -3 in December 2008 and 0 in 2009 and has been warmer than zero from 2009-2012. December 2011 and 2012 have both been much warmer than average with St. Louis only dropping to 20 in 2012 and 19 in 2011 and Kansas City dropping to 7 in 2012 and 9 in 2011.
The sun is at its lowest and dimmest this month of the year in the mid latitudes.
Although we lose daylight in December, things begin to turn around by the end of the month with 90 minutes of daylight gained between the winter solstice and the 21st of February.
Snowfall since 2008 in St. Louis during December has generally been below average. Only 1 year, 2010, recorded above average snow. 7.9″ fell that year. The least recorded was a trace in 2011. Since 2008, December snowfall in Kansas City has generally been below average with two exceptions. 6.2″ fell in 2008 and 15.1″ in 2010. 2011 marked the year with the least recorded, only a trace.
Snowfall in December averages 4.4″ in St. Louis and is typically the second snowiest month.
Snowfall averages 4.6″ in December and is typically the second snowiest month of the season in Kansas City.
Due to the prevalence of (relatively) cold and dry air, December is a dry month, with less than 3″ of rain at STL and less than 2″ at KC. Since 2008 however, 3 of 5 years have recorded above average rainfall (or melted snow and rainfall) at St. Louis, and all of those years had totals over 4″. The “driest” year was 2009 with only 1.30″. At Kansas City, 4 of the past 5 years have recorded below average rain or rain and melted snow. The driest year was 2010 when just 0.52″ was recorded. Even the year with 15.1″ of snowfall still recorded below average liquid equivalent water for the month.
The chances of a “white” Christmas are typically low, generally 10-25% on any given year. The region’s location at the southern edge of the mid latitudes and for Southeast Missouri and S Illinois, just outside of the subtropics (The subtropics extend from 23.4 north to 35 degrees north) mean it is typically quite difficult to get the elements to come together in the right way to produce the 1″ of snow or snow on the ground on December 25th to qualify.
Average annual snowfall totals for the region are low enough to be within range of one to two significant snowstorms, or even one snowy month. Kansas City’s 2010 December snow total, for example, was 15.1″ which was almost an entire season’s worth of snow in one month.