Winter severity index shows few real trends
In 1975, Wisconsin began to keep track of the severity of winters in the northern third of the state. Our severity index was arrived at after testing several different procedures.
We presently use the number of days with a minimum temperature of zero degrees Fahrenheit or below as a measure of winter air chill and the number of days with 18 inches of snow or more on the ground to estimate the snow hazard. Days when both conditions occur together are scored a two.