Hello, Rickjo!
Pin Oaks need a fair amount of water, but not swampy conditions. Is this one growing in the eastern half of the country, where it lives off of rainwater? Or in the western half, where irrigation is the norm?
If the former, how dry has the weather been over the summer? Severe drought could cause it to drop its leaves early, maybe with less than the usual fall color. Flooding could also cause the leaves to drop, especially now.
If the latter, how has your irrigation system--i.e., lawn sprinklers, hose, drip system, etc.--been functioning? Did you leave the watering in someone else's hands while you went on vacation? Was there a long power failure which may have reset the clock on the system?
In California through Oregon, another possibility may be Phytopthora ramosum, a fungus that attacks the foliage, though it is usually more prevalent in rainy spring weather. A few other fungi may attack Pin Oaks, but a local arborist will be better able to diagnose them than I would.