I have a window in my craft room. This is also the room where my computer is. It's not is real good shape and mostly covered with plywood. This past summer we cut a hole in the plywood so we could have more ventilation. The USA map is taped on the glass over where the hole is in the plywood. There is a LOT of cold air that comes in the window at night.
Sitting next to the window at my computer gets pretty cold some nights already. I can only imagine how much colder it's going to be once the snow starts falling.
I found an old quilt and a board that was just the right size to fit in the old blind holder. I shoved the top of the quilt over the board and tucked it in on both ends. It's long enough there us a good amount there on the window sill. It may be old and torn but it sure does a good job helping to keep some extra cold air out. One more step to being warmer.