The Last Happy Hour: Instant Winter Severity

Winter Severity Index

During the past 24 hours, we’ve been getting walloped by our first major snowstorm of the season.  We’ve received at least a foot of new snow on top of what we already had.

Meanwhile, today is the last day of Wisconsin’s gun deer season.  Bow season began back in September, and continues until January 9.  In October, gun hunters in some deer management units had an early four-day antlerless season.  In November, we had the regular nine-day gun season, followed by a ten-day muzzleloader season that just ended Wednesday.  Thursday morning, persistent hunters could head back out with their breechloaders for a four-day late antlerless season that will end later this afternoon.

It’s not easy being a deer.  True, all this new snow will keep most hunters out of the woods today.  But sometime early this morning, we crossed a threshold.  The weather officially became severe—doubly severe.  Last night the temperature was around ten below, and we now have over 18” of snow on the ground.  If this keeps up, we’ll have a long, severe winter. 

Wildlife biologists measure such things with a tool called the Winter Severity Index (WSI); according to the WI DNR, it’s calculated by “…adding the number of days with 18 inches or more of snow on the ground to the number of days when minimum temperatures were 0 degrees Fahrenheit or below between December 1 and April 30.  If you think of it as adding up points, a day when both conditions occurred would get two points.  At the end of the winter all the points are added up, resulting in the WSI number for the whole winter. A winter with an index of less than 50 is considered mild, 50 to 79 is moderate, 80 to 99 is severe and over 100 is very severe.”

The WSI isn’t perfect; 17” of snow topped by an icy crust doesn’t earn that day a second point–no matter how unpleasant conditions might be for cold, hungry deer.  Similarly, there’s a big difference between one below and forty below.  Still, the WSI at least allows rough comparisons from one winter to the next.

So far this month, it’s been below zero about every other night.  Five points right there.  Just checked the forecast; more subzero nights on the way.  Looks like we’ll be racking up two points a day until later in the week.  By then, we could be getting more snow. 


Author: alcambronne

Retired photographer, author, and cancer survivor living in northwest Wisconsin.