I'm in VA, so it doesn't get that cold here, but my rainbows come in from CA. They probably do a pit-stop in Chicago on the way here
Anyhow, the guy I buy from on AquaBid asks that the temperature of the bag water be taken as soon as you open the box, and that you email that to him along with the temperature outside. Smart man.
Last shipment I got in the temperature was 46* outside (hey, it's VA) and the temperature of the bag water was 75*.
Like I said, it's VA but who knows where the plane actually went in the last 24 hours?
IME when you get the fish, immediately open the box, take the temperature of the bag water and take out a sample of the water so you can check the ammonia level. Then IMMEDIATELY add a few drops of Prime or Amquel+ to detoxify the water. It will help the fish immensely and increase the success of acclaimation.
Make sure you write down the temps and ammonia readings. If there are any problems with the fish you then have data to back yourself up. You never know when you will need it.
Roan