"Fall is a great time to seed"
Early fall is a good time to start applying selective herbicides to control weed issues. Once you you've reached your desired level of weed control in the fall, you have a great time to over seed. If you don't over seed something will simply grow in to fill the empty space.
Ground temperatures in the fall are still good for seeding. Fall temperatures are cooler, enabling less water and reduced disease issues. Another benefit is fall usually provides less weed competition than your spring plantings.
According to Target Sales Rep and Seed “Specialist” Gary Willis both Tall fescues and Kentucky bluegrass usually require high heat units to germinate. He usually suggests planting those species by the middle of September. Remember both of these species require 16 weeks before beginning to introduce them to light traffic. They also take longer to germinate than perennial rye and fine fescues for example; so plan ahead.
For many Perennial rye 3-way blends are widely used in Sports turf, Golf, and Landscape. Quick to germinate, good wear tolerance, and typically need only 6 weeks for light traffic. Target always recommends blue tag certified seed. Blue tag seed establishes your assurance of genetic purity and germination of varieties, blends and mixtures. They produce dense, attractive, fine-textured turf with bright, dark green color.