Hi Pat,

I sell Japanese irises up here in Z6. I wouldn't do it now. I would wait until early spring, or if you don't want to miss some of the bloom, you can wait until after they bloom next year. Japanese irises can be divided anytime in the spring, summer or fall, unless the weather is going to be over 90 in the few weeks after, providing you can keep them wet.

You're too close to ground freeze at this point to be sure they will establish good new roots. It takes about 6 weeks.