There are a lot of Clematis that color, I have at least six so hard to say which one it is. None of them bloom all summer like annuals. You can cut the seed heads off and cut it back and fertilize it and you might get a second flush of blooms.....

Clematis 'Stasik'? Just a guess.

After more research I believe it's a Etoile violette clematis. Hoping for a second bloom but not counting on it ;)

Looks far too red for EV unless the color in your photo is really off. EV is purple. Is yours blooming now? EV is a summer bloomer here. Also, EV has cream or yellow stamens which yours doesn't appear to have.

IDing a clmeatis isn't only a matter of color. Look at the boss of stamens in the center - color, shape, and size compared to the petals. Look at the overlap or gappiness between the petals. Look at whether the petals remain flat as they age or tend to curl in some way. Look at whether the petals are ruffled along the edge. Check out the flower size. Leaves on some plants are characteristic, either in color or shape. See if the plant is a climber or herbaceous and how tall it is supposed to get. Sometimes bud shape, flower stem length, or bud size are important. Season of bloom will be moderately consistent in a given area, so a plant that blooms here in NH in May I won't expect to be blooming in July here.

Where are you?

I'm in Chicago. The picture is off- it's a very deep purple with cream stamens. But this did bloom in spring so maybe it's not. All is good- I'm thinking about moving it as I have a small garden and it's a focal point since I thought it was to bloom all summer. Can you tell I'm new to clematis world? ;)

I find the seed heads ornamental, so you might want to consider if those silvery puffs will suit instead of flowers for part of the time.

For all summer flowers, black-eyed susan vine (thunbergia) and mandevilla, a tropical vine, have had the longest flowering season for me.

Same here. I plant both- mandevilla and BE Susan vine and have success as well. June thru October which is so great. Here is a not great picture from last year mandevilla

It is not Etoile Violette. She is a type III with small 2" flowers. That appears to be a Type II large flowered hybrid. Even if the color is off in your photo there is no way it is Etoile Violette.