Fall is best for planting cool-season grasses like perennial ryegrass, tall fescue, and Kentucky bluegrass. Daytime temperatures should be averaging between 60 and 85 degrees which translates to soil temperatures between 50 to 75 degrees.
Warm-season grasses, like Bermudagrass, Bahiagrass, Centipede grass and Zoysia grass has the most successful germination rates in spring and early summer when daytime temperatures are averaging about 80 degrees. Overseeding warm-season southern lawns with cool-season grass should be done fall.