Coldest First Week of December on Record

Temperatures for the first eight days in December 2005 were significantly colder than any other start to December in recorded history.  Temperatures over the past eight days averaged just 0.9 degrees in Sioux Falls and Huron, which is nearly 21 degrees below normal.  The story is similar for Sioux City as well, with an average temperature of 4.3 degrees, which is 21 degrees below normal.  Other seasons with abnormally cool early December temperatures include both 1972 and 1978, but this year’s averages were two to five degrees colder than both of these years.

The following are the most consecutive days with highs of 15 degrees or below at Sioux Falls for any month in the last 20 years in reverse chronological order...

8 days  12/1-8/2005
8 days  1/27-2/3/2004
8 days  1/13-20/1994
12 days 12/11-22/1989
8 days  1/13-20/1984
14 days 12/16-29/1983

The all time record is 20 days in a row of 15 degrees or below from 12/27/1911 to 1/15/1912. Note the last time we had 8 days or more of 15 or below in December was in 1989, 16 years ago. December 2005 is earliest in the season we have had this record however.

The worst continuous extreme cold for any month of the year was in December 1983. The temperature was zero or below for 9 straight days from 12/16-24/1983.  Lows were mostly in the 20s below zero with many record lows and low maxes set. The high and low on Dec. 23rd were -14 and -25.

 In addition, the fall of 2005 has a few similarities to the fall of 1978. Both of these seasons had very warm periods in September, dry Octobers (outside of one rain event on October 4th, 2005) followed by a very cold stretch in early December. The winter of 1978-1979 proved to be one of the coldest and snowiest in recent history, with temperatures around 15 degrees below normal in both January and February and above normal snowfall each month. 

 Local studies conducted at the Sioux Falls National Weather Service office also support increased chances of a cold and wet winter for the area. These studies indicate higher probabilities for below normal temperatures for December, January, and February. They also show a better chance of normal to above normal precipitation in December and January, and near normal precipitation in February. These local studies are still being developed and tested, but have shown some skill in forecasting 30, 60, and 90 day temperature and precipitaiton anomalies. They are based on 9 climate indices, and observed temperature and precipitation data for the past 54 years.















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