Fall is the best time for renovation and seeding of cool-season lawns. Temperatures are currently above normal for early September, but history suggests that the weather will moderate within the next few weeks.
Remember that spring-established tall fescue is more susceptible to drought, heat, fungal diseases, and weed encroachment. With normal summer weather patterns, spring seeding is not likely to result in a year-long stand of healthy tall fescue. So do not delay, seed in the fall! If you must wait until October there is an increased likelihood of slow/low germination.
Before seeding, core aerification is recommended to reduce compacted areas. Getting good soil to seed contact is paramount to maximize available soil moisture. A typical tall fescue seeding rate is 5 to 6 pounds of seed per 1000 square feet. Germination will normally be in 7 to 14 days with soil moisture and suitable soil temperatures.
Since seeds and seedlings may be damaged by some herbicide applications, fall seeded cool-season grasses should not have any herbicides applied until it is extensively tillered.