Grass can be cut in winter during mild weather. However, grass does not generally need to be cut during the winter because it does not grow very quickly in cold weather. Typically, grass should only be cut in winter in warmer climates.
If a lawn needs to be cut during the winter, it should only be cut when the ground is dry and there is no frost in the forecast. The best way to maintain a lawn during the winter is by properly preparing it in the late summer and fall. About.com recommends cutting grass shorter gradually as cooler weather approaches.