Wrennie, you can plant
Iris any time... but if you wait for too long & don't get them in until spring
, they might not get their roots settled in soon enough to give you any blossoms. (Mine bloom in late April/early May.) They'd be better off in the ground, but they're pretty draught tolerant, so if you're going to get them in within the next month or so, you don't really have to do anything special with them. I have some in my garage that I haven't gotten around to getting planted. They've been there for a month & still look good.
Remember, when planting Iris, dont completely bury the rhizome. Leave the tops exposed, & make sure you put them in a place where they'll get good drainage. If I'm not mistaken, Iris in your area are susceptible to root rot if their feet are too wet.
(Oops! you didn't say what type of Iris they are... I'm assuming that they're Tall Bearded.)
If they're bulbs & not rhizomes, you need to totally bury those.