Continue to keep the leaves off your lawn, especially on cool-season lawns, because they continue to photosynthesize during the winter. We have the tendency to let the seemingly ever-falling oak leaves build up during the cold days of winter. On a dry, warmish day, you can mow both cool- and warm-season lawns to help groom the lawn and mulch the leaves. Avoid heavy traffic on cool-season lawns when it is cold enough for the grass to be frozen. Frozen grass is easily broken and the crown can also be severely damaged.