The severity of cold weather and heavy snowfall during the winter can impact the survival rate of the deer population in the area.  Department of Natural Resources Conservation Warden Chris Kratcha says the DNR typically uses a winter severity index that tracks the number of days of 18 inches or more of snow that is on the ground and temperatures dropping below zero.  He notes that the combination of snow and extreme cold over the course of many days can really be dangerous to deer, especially fawns later in the winter. 

Kratcha says every animal has its own adaptation for survival, and that it is remarkable that many can survive in extreme weather conditions.