Walnut trees just dropping leafs - weather indicator?

[DeeDubya]

This is evident here in Texas with the drought. Some trees started dropping leaves in August, gradually shedding them as the drought continued. But some "not so hardy" trees like Hackberry just died with all the leaves still on. The all too abundant Cedars don't change in appearance. They can suck the moisture out of rocks. I think in a continued drought they would be the last to go.

I'm quoting a misquote... I've got a patch of about 10 large cedars (15' or so) that are dead as a fence post. They're not as hardy as I thought.