I would chop it back hard in early spring. Some detangling and thinning of the longest stems can be done now for cosmetic purposes, but it probably isn't long before it goes to sleep for the fall there.

It'll keep flowering into October and i cut mine back by about 3/4 as i deadhead for the last time, then.
I don't cut it in the spring though because it doesn't emerge until early summer.

I keep forgetting that our spring (February-March) is like your early summer!

Our weather patterns are all over the place lately, Tug !
I think we're wondering what kind of winter we'll have 'this' year .... and hoping like mad that it'll not be another bad one :-/