I am sure it is not (the norm) for plants in his area to be yellowing this early.
He has just had a extreme weather year (in his area).
I on the other hand (over in Southern Middle TN) have had a very good year. It has been hot some, but we have not really had any long hot and \"DRY\" spells. We have had good rains all season. The grass and trees here are still nice and green... sort of look like early June condition... but it is the end of July.
Hugh obviously has had worse than usual conditions in his area (Same State as me)... but he is in East TN.
A couple years ago, we had some extreme heat and dry at the end of June here... and some of my seed producing bed plants started yellowing.
They are at the mercy of the weather... and long spells of heat with no rain will sure stress them out and make em turn in early.