Some grass seeds will burn in direct sun, they use up their food supply too fast in the heat and that is the reason your lawn goes dormant. Check with the Seed package to see what seed is best for your area. Kentucky Bluegrass varieties require much more upkeep than other seeds. Mowing, fertilizing, and watering are the steps you will be performing more than usual with Kentucky Bluegrass. Know your seed.
Perennial grasses survive season after season, producing and growing.
Annual grass seed produces only for one year, at the time of planting and at the end before the grass dies. Then you have to remove any excess dead grass from your lawn and plant Perennial seeds to take over, which is much more time consuming and a lot more work. If it happens to get too cool when you finally plant your lawn, try laying hay over the planted seed. The seed will stay moist and warm and grow much faster. When the seed starts to grow and reaches a few inches in length, time to use a fertilizer.