Its hot hot hot at the Jersey Shore. We spent days cleaning up the yard after the harsh freezing winter we had. Everything looked great outside for a while anyway. Now it has been so hot my grass is fried brown and dead. My flowers are screaming for some rain, even though I water them, its just hot.
No doubt about it, hot weather is always a trying time for plants. Grass has a tendency to go dormant during a heat wave, to preserve what little water it has until it gets replenished.
Have you given the grass a thorough soaking? Is it still brown? If so, you probably have a grub or cinch bug infestation. If the damage is really extensive, you'll have to dig it all up and re-sod or re-seed the whole lawn.