Question
I have a 15ft-20ft tall live oak in NE Florida.  The tree appears healthy (new growth and green) except quite a few leaves are really hard (to the point of crunchy), shrivling/curling, and bumpy but uniformly a lush green.  Could it possibly be wide swings in heat/humidity related (i.e. scorching temps followed by cooler rainy weather followed more scorching temps)?

Answer
I can not ID the problem from the information you sent. I would suggest you contact the Florida State Forestry agency and ask one of their Foresters to come take a look. This is a free service. Florida has a Pathologist and an Entomologist on staff and if the Forester can not ID the problem they can call in the Forest Health Specialist.
Here is the web link to their contact page for the county foresters.