I do more "serious" walking - i.e. going out to do planned day walks as opposed to summer wanders - between October and March than I do at any other time of the year. I love walking in bare woods, hearing the wind moaning in the tops of the trees, and watching wildlife survive; I like the greater solitude at this time of the year too.
There is a proviso, however. The temperature needs to be in double figures for me to go out on such a walk. Even though I'm wrapped up in baselayers, full warmwear and a windproof top, 8-9C might just about be acceptable but anything lower than that and I get no pleasure out of it, I don't see the point in it and I would rather be at home in the warm.
One thing I absolutely fail to understand is how people can enjoy going for a walk in the snow, but that's just my personal view.