Strange Phenomenon

I don't know what this means, but if any of you do, please tell us all.

Hereabouts, in Kansas, the black walnut trees are the last to leaf out in spring.  All the other trees have leaves blowing in the wind by the time the walnut's are growing and grown. 

I grew up with them in the yard of my parent's house. 

Here we have several black walnut trees.  One has stopped producing, the Century Tree:

As you can see, it's dying.  The trunk has even started shifting. We upgraded our insurance on the outbuildings, just in case.

This one shelters and shades the big henhouse:

But I noticed in the last few days that these trees... the last to leaf out in April of all the trees... .

are dropping their leaves already!

This is a random example.  As I cut grass tonight (doing 90%  of the mowing since it's supposed to get stifling hot this weekend)... I noticed along the north fence line that many of the trees there have been dropping leaves.  It's only July 8th for pete's sake! We have had a normal rain year, and only a few days of very bad heat, though we have about four coming up here starting tomorrow.  I do not remember leaves dropping this early, ever... at least ever that I paid attention to!
I noticed that there are many leaves down from the dying tree, as well.  Many years ago, wood companies would come in and take down walnut trees for free, but it will cost us about $1000.00 to take this one safely down, and send the wood away to be used somewhere. 
I wonder if the leaves falling so early is a prediction of weather to come?