You should plant them as soon as they arrive.
Here is a list of reputable vendors from the American Iris Society (link).

Here is a link that might be useful: Commercial Directory

Tammy, nurseries will ship when the time has come to dig in their location. You can specify a later ship date, and you may get freshly dug rhizomes, or not, or they may run out of the variety you ordered.
Walter Moore has promoted a method for handling the 'I got iris shipped when it was too hot to re-plant" situation. Basically you pot up the rhizomes into 4" pots with potting mix and place them outside in the shade - watering frequently. When the day temps are in the 80's or less with temperate weather in the future it is safe to plant them out. Planting Rhizomes when it is over 90 -100 in full sun may lead to them rotting before they get growing. If you have to plant under these conditions - make some kind of shade - even a shingle stuck into the ground on the South side is helpful.

Thank you both for the advice! It does get into the 90's here on a daily basis during the summer here. Ill be sure not to plant in full sun until closer to fall, but I have quite a bit of gardening space in partial afternoon shade as well. I placed an order with Blue J's and Burgards.

Boy is there some pretty iris out there!

Tammy

I think Shreiners are the best of the best and include a booklet on how and when to plant thats a huge help for newbys to iris. I,ve been buying from them for many years and they are really quick to take care of any problems and replace any iris that don,t make it in the first year.

Wild Iris rows is very good, very generous! It's confusing that their is 2 companies with close to the same name.

Also lakeside iris is great, 760-378-3841. No internet site

With you being in East Tn..there are 3 near you...and if the iris grow good for them, then you know they should do well for you.

Iris City Gardens..outside of Nashville
Wild Iris Rows Springfield TN
Rocky Top Gardens

And I can tell you I got beautiful plants from Rocky Top, and much bigger ones than some better know nurseries give.
kay