As nights get colder and colder, remember that lawn grasses continue to grow throughout much of the fall, usually only stopping when temperatures remain below 50˚F (10˚C) or so for a good week. Even a first light frost will usually not stop them. So, in many areas, you will still need to mow into November or even later, although less frequently than in summer.
However, when the grass finally does stop growing, it’s time to mow one last time… and shorter than you did all summer long, too, at about 2 inches (5 cm) in height. And for once, collect the grass clippings (you can put them in the compost or use them as mulch). This will help to better aerate the lawn grasses, making them more resistant to winter damage and especially to the diseases that often set up shop under the cover of snow.