The winter season represents the coldest part of the year in the northern hemisphere, when daylight hours are at a minimum and darkness lasts all day long in the high latitudes. Average winter temperatures (as defined as December, January and February) are just below freezing in Kansas City and a few degrees above freezing in St. Louis. The coldest winter temperatures were recorded in December, 1989 when readings dropped to -23 in Kansas City and -22 in St. Louis. Very warm days can also occur, particularly in late February and 1972 was an example of this when low to mid 80s were recorded. Winter is also a drier time of year with less moisture available to work with and despite high snowfall totals, liquid equivalent moisture is just around 4″ in Kansas City and 7.5″ in St. Louis.
Daylight reaches a minimum at the winter (southern) solstice and begins an increase early in the season, but as with the summer (northern) solstice , temperatures lag the change in daylight.
This graphic shows the waxing and waning of daylight during the year from the summer maximum to winter minimum. A difference of over five and a half hours of daylight exists between the two.
Winter also has a very low sun angle compared to the summer. The sun rises in the southeast and tracks low in the southern sky and sets in the southwest. The low sun angle means the light must travel through more atmosphere than in summer and this results in a more reddish and weaker light compared to the bright, harsh, white mid day summer sun. This weaker light is less able to deliver heating to the earth’s surface as the sun’s rays are spread out over a greater area. It may seem counter-intuitive, but the earth is actually at it’s closest to the sun in January and because of that, the orbit is at it’s fastest.
St. Louis average monthly winter temperatures. Only 1 month, January, is below freezing.
Kansas City average monthly winter temperatures. Two months, December and January, are below freezing.
St. Louis winter precipitation totals show a slow decline through the winter season.
Kansas City winter precipitation totals are all less than 2″ and bottom out at just over an inch in January.
Kansas City monthly snowfall averages:
This graphic shows average yearly snowfall accumulation (as measured from July 1 to June 30 of the following year). Average annual snowfall in Missouri ranges from 18-24″ north to just 3 to 6″ in the Bootheel. Average annual snowfall in Illinois ranges from 36-42″ in the lake effect snow belts around Chicago to 3-6″ in extreme southern Illinois. Kansas City an St. Louis both lie in the 12-18″ belt while SE Missouri and S Illinois lie in the 6-12″ belt.
Here is a listing of the top 10 snowiest winter seasons in St. Louis and Kansas City. 1911-1912 is the undisputed all time record snowiest winter in both cities. The snowy winter of 2010-2011 ranks as #6 in St. Louis and #9 in Kansas City, while 2009-2010 ranks as #4 in Kansas City. The top ten snowiest 24 hour periods are shown for St. Louis and the top 10 biggest snow storms are shown for Kansas City.
On the flip side, the top ten least snowiest winter seasons for both cities. The “non” winter of 2011-2012 ranks as #10 for St. Louis but as the all time least snowiest winter for Kansas City.
Snow and Christmas go hand-in-hand in most people’s minds and that may be true, but not so much for our part of the Midwest. In any year, statistics bear out that there is only 10 to 25% chance for a White Christmas (as defined as having at least 1″ of snow on the ground). In other words in any given decade, 1 to 4 years may see a white Christmas and in any given century 10 to 25 years may have a white Christmas.
Due to the cold temperatures in winter, there are added challenges to deal with. Summer time rains can be a nuisance, but outside of flash flooding and severe weather, which can be devastating on a local scale, winter storms can and frequently do impact a large part or all of the Midwest.
Winter conditions can depend upon larger scale weather patterns which may last all or part of a season. The biggest and most well known are El Nino and La Nina. This winter neither are expected to be a major influence which leaves shorter-term atmospheric patterns to take the lead. These patterns can work independently of each other or in concert with each other.
The first of these is called the “Pacific-North American” pattern. It has a positive and negative mode. The graphics below show generalized weather conditions which can be expected for each mode.
The next pattern is the Arctic Oscillation. Like the Pacific-North American pattern. It has a positive and negative mode. The graphics below show generalized weather conditions which can be expected for each mode.
A third pattern is the North Atlantic Oscillation. Like the the previous patterns. It has a positive and negative mode. The graphics below show generalized weather conditions which can be expected for each mode.