Whether you hail from Seattle or St. Louis, certain seasonal adjustments are no-brainers. You swap the light trench for the woolly overcoat, stow the window screens, and top up the antifreeze in the car. So why, when it comes to skin care, do you expect the same old routine that worked for spring, summer, and fall to carry you through the icy months? Winter's low humidity and harsh wind chill can affect your derm in different but no less devastating ways than blistering heat and sun. So, unless you aspire to the cracked lips, snow-burned hands, and ruddy cheeks of a competitive mountaineer, follow this skin-saving Rx recommended by top experts from around the country.