As long as it stayed dry I wouldn't worry about it. Ammo doesn't like to be heated or cooled rapidly, it's the sudden changes that cause problems. If it was cold for a while and then warmed slowly, you should be fine. Give it a good look over and if there is any question about a round or two, don't shoot it.
If the pain is lacking so is the discipline...
"the only 911 call I need is chambering a round" - Mr. Muller, MO car dealer