Cold Bullets

Good buddy and avid hunter Tommy Allen sent me what I thought was a blog saying that extremely cold weather slows bullets down. I called Sportsman's Warehouse sales associate Thomas Vigil to get his thoughts. "Cold can slow bullets. A cold bore shot with extreme cold, yes, metal seems to contract a little bit so it will slow the bullet down, metals seem to contract a little bit when they are cold and expand when they are hot. After the first shot, if you are shooting regularly, you are good to go. So what would you recommend given that, let's say I'm out hunting and I see an elk, it's extreme cold, I want to be quiet, what do I do? I would shoot a here high. You have bore sighted your gun at 100 yards, I'd shoot 1/2 inch high.