When it comes to deciding when to aerate a lawn, it's true to say that timing is everything if you want to get the best results. As we'll go on to explain in more detail, early autumn is a prime time to complete this task for a number of reasons. Doing it at this time of year will give your lawn a real boost by letting in more air for healthier roots, improving drainage to avoid waterlogging issues, and resulting in faster uptake of nutrients.