While Wednesday was well above average in Sioux Falls, if we didn't have any snow on the ground the temperatures would have been even warmer.
This is because the snow reflects a lot of the sun's radiation. Ground without snow soaks up the radiation which in turn warms the bare ground a lot easier.
The National Weather Service in Sioux Falls did a study on the snow's affect on temperatures and here's what they found. It was broken up into different weeks through the winter months due to the change in the sun angle.
During the second week of December, with no snow on the ground, Sioux Falls' warmest highs are 61, 59, and 57. Add just a trace to an inch of snow and the warmest highs are 53, 50, and 49. Two to five inches of snow and the highs fall to 47, 45, and 44. Six inches or more and you have temperatures falling to 39, 38, and 33.
We officially have two inches of snow on the ground in Sioux Falls, after Wednesday's warmth I wouldn't be surprised if it goes down to a trace by Thursday. But more snow may be on the way for this weekend.