In the fall, turf roots grow long after the grass has stopped. Feeding the roots with natural growth fertilizer will boost growth in the spring.
Fall is the another window of opportunity for the application of lime (if needed) and compost. A good shot of compost now will help prevent germination of weed seeds in spring and give the turf.
Summer stressed lawn needs to be aerated and seeded. The best time to seed your lawn is late summer and early fall when temperatures are cooler.