That depends on the type of irises you're asking about and the size of the rhizomes. Bearded irises can sometimes survive for many months out of the ground if the rhizomes are large with plenty of stored energy. Small rhizomes will last proportionately shorter periods of time out of the soil.

Beardless irises should be replanted as quickly as possible, and most should be kept in a bucket of fresh water until planted.

Laurie

If you have some irise rhizomes that have been, say, lying around in the garage all winter, go ahead & plant them.

If you plant them, they may or may not grow (but in Louisiana, I'd bet on most of them growing).

If you don't plant them, you know they won't grow.

It's always a good idea to plant them ASAP, but...

A woman in my neighborhood found a box of iris rhizomes in her garage one June (hot in Texas).
She had dug them up at her old house & moved them to the new house the previous August (hot in Texas).

She planted them.
Most of them grew.

I never throw away an iris rhizome that seems like it might be viable, unless it also looks like it may have something contagious.

Then I toss it into the compost pile.

An iris is absolutely flourishing in the compost pile right now.

Plant 'em & see what happens.

Best luck!