It could be Ville De Lyon, which has rounded petals like that and is about that color. Mine is now blooming for the second time this year, and I don't remember a year where it has done that before. It's one of my favorites.

Ville de Lyon has a really vibrant color; if you post a closeup of one of the flowers, it could help.
Here is a photo of Ville de Lyon, earlier this season. See if it corresponds to yours.

thanks true-blue and Ophelia. The clematis belongs to my sister and its hard to get a good photo of it now. There are no new blooms on it to photo now so maybe I'll give it a try next year. This was the first year that it bloomed and didn't have a lot of blooms.