Why can't I just start tackling the big clumps with a lot of rot starting now?
I don't plan to divide into individual rhizomes, just small clumps.

You can scoop out the rot & apply a bleach drench. We do the time wait to allow them to go dormant.

I had a good friend here that raised a large iris garden, over 400 cultivars, and he insisted on starting to replant right after bloom season. He replanted every year. His iris grew well, bloomed well the next year, and he donated countless rhizomes to our Utah Iris Society Sale each year so it can be done.

That's encouraging. It is such a big job it feels better to spread it out. When I wait, there are often many patches left untouched for yet another year. I've done it before with certain clumps that needed emergency help and they did well.

Constant off & on rain here makes it difficult to see in the garden. Listing irises for dividing for the club iris sale.