Depending on the weather, the time when you should stop mowing your lawn can differ greatly from one area to the other. Climate conditions will generally dictate the exact date when your lawn will stop growing, and that is usually the time when you should stop mowing and focus more on overwintering your lawn and making sure it can make it through all the way to spring.
The main issue with mowing the lawn after it stops growing is that it will no longer grow back to an ideal height. This can make your lawn quite vulnerable to the harsh winter conditions and temperature, and may expose it to disease or even kill it.
The best thing to do is to observe your lawn and do some research on the local climate. Typically, temperatures have to reach a certain, critical level in order to induce a state similar to hibernation in your grass. This will trigger it to slow down its growth, which will be your main clue of when to stop mowing your lawn completely.
In some cases, this time can come as late as December, especially since most experts will still recommend that you continue using the mower to mulch some of the leaves on your lawn until around that time. Find more answers of when to stop mowing and when to fertilize lawn in Denver from local lawn care companies.