Question
Hi,

Thank you so much for the quick and detailed explanation.Its very informative.I was not sure where to send you this thankyou note...so i had to write it here.

I really hope that there is no disease/bugs as we have no experience in this regard.But we have had temperatures that go up to 85-88F during daytime and night it cools really quick to upto 55F.  I hope this is the cause.Meanwhile when i said the grass is brown...it actually looks dried and is like straw.We have a lot of fire ants problem And we treat the mounds as and when we see it.

Thanks once again for your answer.Appreciate it.

Norma  

Answer
You are welcome.

Dried (died) straw looking grass is dead.
55F nights and 80-90F days are not too cold for the grass to grow. Nights into 30F or 40F would be too cold. I suspect problem is with insect or disease. My initial guess is probably insects. Sorry, I know this is not what you wanted to hear, but that is my offhand assumption without seeing the lawn.