Interesting, because mine did the same and I live in SW Missouri.
In the Spring all 4 of my Clematis were doing beautifully and then they started going brown, quickly. These plants have been in the ground for 5+ years, so they're definitely not new. They have all previously grown very well.
Throughout the summer I would see little parts of my plants with some green and a flower or two, but the vast majority of the plant was dry and crunchy....
Anyone have any ideas on what happened??