Follow how harsh each winter season is using this Winter Severity Index

Beyond The Forecast

(WFRV) – As the frosty chill of winter gets closer and closer, a lot of people often wonder how brutal our winter will be here in Northeast Wisconsin. 

There is an index from the Midwest Regional Climate Center that measures how harsh each winter season is as it happens. The metric is called the Accumulated Winter Season Severity Index (AWSSI).

Every day, scores are calculated based on high and low temperatures, snowfall, and snow depth. Scores are then added for every day through the winter season which is not limited to just meteorological winter.

Points can start to be accounted for the first day of snowfall, the first day with max temperatures 32 or below, or December 1.

The point system is complicated to follow, but understand that colder temperatures and large amounts of snow equate to more points. Say our high temperature was 0 degrees, the low temperature was -10 degrees with 1” of snow on the ground, that would be 15 points on that day that would contribute to the seasonal total.

When the points are added up as the winter season goes on, they are ranked based on historical percentiles dating back to 1950 to show how severe the season is. For Green Bay, our 80th percentile score is 1360, meaning anything higher would be an “extreme” season. 

Our highest score on record qualified as an extreme score of 1809 in 2013-2014. That winter gained a huge amount of point thanks to cold temperatures in January. Plenty of snowfall to start the year allowed that winter season to be the highest AWSSI score. 

The AWSSI score can change as the season goes on. For example, in Green Bay we could start with a harsh December that would have us in the Severe category, but a mild January and February could make our season average. 

In the last five seasons, Green Bay has had two mild winters, one moderate winter, one average winter, and one severe winter which was the 2018-2019 season.  

If you are curious to see who has the highest AWSSI scores across the country, check out the median scores across the United States. Our friends up in the Upper Peninsula of Michigan tend to have some of the most brutal winters compared to the entire country. 


Some limitations in the index include the fact it does not consider mixed precipitation or wind chill. Overall, it may be a great metric to keep track of as our winter season gets going in Wisconsin.

Go to the website and track where we stand right now in Wisconsin here.

Copyright 2021 Nexstar Media Inc. All rights reserved. This material may not be published, broadcast, rewritten, or redistributed.

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