National Weather Service United States Department of Commerce


On the heels of a major winter storm just a week before on Dec 12-16th, Arctic cold air settled in across the region beginning on Sunday the 18th with high temperatures for most of 5 degrees or colder each of the next consecutive 6 days through the 24th. Low temperatures dropped into the minus teens. An unusually potent blast of cold air for December followed in behind a reinforcing Arctic front Tuesday night, Dec 20th, into Wednesday, Dec 21st, along with a trace to as much as 2 to 3" of new snowfall on top of the pre-existing snow pack. Wind gusts of 35 to 55 mph behind this front impacted the region from the 21st through the 23rd, resulting in an extended period of life-threatening wind chills in the -35 to -60 degree F range and ground blizzard conditions. A ground blizzard is a blizzard, but does not involve any new falling snow. 

The extreme cold made the threat to stranded motorists even more dangerous, as numerous roads became impassable. Nearly the entire state was virtually shut down, for the second time this December, as roads were either deemed "No Travel Advised" or closed by the SDDOT. I29 closed from 6pm CST on Thu Dec 22nd from Sioux Falls to the ND state line until 9am on Fri Dec 23rd from Sioux Falls to Watertown and until noon from Watertown to the ND state line, and I90 closed from Rapid City to Chamberlain from 6pm MST on Wed Dec 21st until 2:30pm on Fri Dec 23rd from Rapid City to Murdo and until 4pm from Murdo to Mitchell. Additional impacts commonly included school closures. Governor Noem declared a Winter Storm Emergency on Dec 22nd, which activated the SD National Guard and allowed assistance from the state to county governments as needed.  

This storm system was wide-reaching, impacting much of the eastern two-thirds of the United States with dangerous cold and precipitation. Among the hardest-hit was Erie County in New York State, which includes Buffalo. As of Dec 29th, 39 people were reported to have perished in the storm there. 

Hourly temperatures from 11pm Tue, Dec 20th through 11pm Wed, Dec 21st (purple represents sub-zero temperatures). 
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