Ideally, you should stop cutting grass in October, but you might be able to stretch to November if we have a particularly warm autumn. However, the general rule of thumb is that you should never mow your lawn if the temperature consistently hits 10°C or less. And you should definitely avoid mowing your lawn when the first frost hits.
It’s important that you follow this rule, as cutting your grass during the winter months could be detrimental to the health of your lawn. Waterlogging or compacted roots could result in brown or dead patches, and your lawn may struggle to recover when it starts growing again next spring.