The redback salamanders (Plethodon cinereus) were less of a surprise - they're basically out all winter if the ground isn't frozen.
More important than the 'don't give up' idea here is the importance of locating hibernacula - where critters spend the winter. I do this by paying attention to where the snakes are in the early spring and late summer and reading the landscape (features, like walls, exposed to a lot of sun) for likely dens.
Snakes generally don't go into a true hibernation like some mammals such as woodchucks - sleeping straight through no matter what - rather they tend to take advantage of warm spells to come out and bask a bit. A professional herpetologist I know once found pine snakes basking at their den in a December warm spell, and I've found garter snakes (Thamnophis sirtalis) and brown snakes at 'wrong' times of year. So, if we get a bright sunny week in the 50s in the middle of the winter, you know what I'll be doing.
