Welcome to squirrel hunting. I'm also from that region. Temperatures shouldn't play a big role unless its bitterly cold and windy then theywill stay denned up. Terrain flat or hill makes no difference, found on both. Camo can be a great help. I found in archery when dressed in camo I can have squirrels within a couple feet unaware of me, but if I go out in jeans and orange vest they will pick me out alot easier. They tend to feed out in the open. Hunting the edges of corn fields can be very productive if there is still corn present. Not much sign to look for other than tracks in the snow, den holes in trees, or leaf nests in trees. Sunny days early in the morning with light windsoffer the most action for me. Hope this can help you become successful. Good luck.