I think harsh winters are over-rated in most areas. Deer handle snow and cold mostly just fine - its when they are overpopluated when problems occur.
We get over 130" of snow every year and the deer herd comes through in decent shape. The snowpack does allow coyotes to take some deer - and they do here. The wounded and the sick generally don't make it. But still I think 40 deer per square mile is about where we are at most years.
I shed hunt an area nearby that hunting isn't allowed - and I'll bet there is 60-80 deer per square mile - and these deer are always over the land's carrying capacity - but even in the worst winters (160"+ snow) most of them make it.