The thought is that heavy snow cover (such as the 5 feet depth we have now where I live) provides enough insulation from severe cold to keep the damn little critters happy and viable. Even though I have had mornings with actual air temp colder than -30F twice during this past week. That is very unfortunate.
Heard that you don't want a snow cover for tick killing, you want no snow and a horrible freeze so the frost goes way down. The snow is insulating. Too bad it snowed first this year!
As someone who had Lyme in 2017, here's hoping the snow melts in S. New England the next couple of days and then we get a few days of brutal cold again. Hard to say where I picked mine up but was more likely field related with the Scouts. I fear tall grass more than being in the trees or above them.