I am not sure of the answer, but are any of these iris rebloomers? Did they bloom in the spring too? I had a reblooming iris that didn't bloom in the spring, but bloomed at the end of July. It is just now making offsets. I have also heard of iris waiting to bloom until a hot spell is over, but I haven't heard that iris wait until it is very hot to bloom!

I have had the same thing happen here. At the end of June during our hottest 2 week period between 100-112 degrees, an iris rebloomed. It is a reblooming iris, but who would have thought it would choose that time. I had another iris bloom about the same time, but it didn't bloom in the spring. Elainelope has a bloom stalk on it right now-it bloomed in the spring & I don't think it is a rebloomer. I don't think it is actually going to bloom, it formed decent buds, but the last few days they look dried out. Very odd year, I've never had this happen before.

A likely cause is light. Light like from a street light or other lights you might have around the house, can trigger irises into blooming offseason.

That is odd. I live next to a cornfield. I don't think there is any light pollution that could be responsible. The day length was probably about the same between when my iris normally bloom, about one month before the longest day of the year, and when my odd-time-bloomer bloomed, which was about one month after the solstice. So light could have something to do with it, I guess.

The rebloomer is fairly close to a security light, but the others that have bloomed are not close to any artificial light source.

Clinging Vine, I would think the ones you have blooming now are rebloomers. esp if this same group bloomed last year also...They are obviously very happy where they are! If you dont want them blooming now I would suggest digging them up and replacing them with only spring bloomers. As happy as they are..they should bloom again this Spring..If you are unhappy because the blooms only last a day in this heat..I would suggest cutting them and bringing them in to enjoy..I only wish I had that problem.
ngraham ..Elainelope is a re bloomer.

Thanks for everyone's help. They didn't bloom at all this spring. I don't think they are re-bloomers. There is a street light on the adjacent property, but it doesn't throw a great deal of light in my yard.

It was an exceptional winter here,very mild... do they need some cold?

I did cut them and enjoyed a few blooms in the air conditioned comfort!

Thanks again.

No, they don't need cold. Just a weird year for irises!