Fall: This marks the secondary growth period of the year. During the early fall, your lawn will begin to green out more naturally and will grow noticeably faster. As the season goes on, your lawn's growth will slow down and it will need less water. However, you may still need to water your lawn occasionally to keep the soil moist.
A couple last things to remember: In most cases, it’s much more beneficial to water your lawn deeply and infrequently, rather than watering lightly and frequently. This will help encourage the roots to grow deeper in the soil, making the lawn much more drought-tolerant. And, as stated earlier, regardless of time of year it is always recommended to water your lawn either early in the morning, or in the late afternoon. Watering first thing in the morning (7 or 8am) is by far the best time of day to water. If you are unable to water your lawn in the morning the second best time is in the late afternoon once the sun is a little lower and it's not quite as hot (around 4 or 5pm). Don't water any later than this though. Watering too late in the day can actually be quite harmful to the lawn. With dropping temperatures and no sunlight, the water will rest in the soil and cling to the grass for too long. This can encourage things like fungus and mold to develop, as well as attract unwanted insects.