When the daytime temperatures drop to the low 50's, you should start adjusting your mower down a notch. The last cutting should be cut to 2 inches in height. This is very important because the colder climate, along with less food reserves being stored in the leaf tissue, helps grass roots prepare for winter dormancy. The lawn will also green up faster in the spring. Of course, spring clean-up will be easier with shorter grass blades. Another benefit to mowing shorter in the late fall, is the prevention of winter-born fungus and disease, such as Snow Mold. Snow Mold occurs when taller grass blades hold in moisture and bend. Moisture evaporates more quickly on shorter grass. It is important to keep leaves off the lawn to limit moisture, as well.