It always amazes me when you think about deer in Canada. They have like 5' of snow on the ground and the deer seem to make it through just fine up there. I know they have larger bodies and are better equipped because of it, but it is still amazing.
As far as deer in my area of SE PA, I start to worry when we get a partial thaw and then the snow refreezes creating a very hard crust that the deer have a hard time breaking through with their hooves.