Almost no matter what you wear, your torso and legs will be fine. I'd wear a thick pair of tights, and a thick moisture-wick top covered with a wind layer. The really important things are what you wear on your neck, feet and hands. Mittens are way better than gloves. Windproof mittens with a little insulation work great. Be sure your shoes aren't mesh, and if they are use shoe covers. And wear some kind of face mask to cover your neck and chin.