Hello Alan. You didn't state a caliber, so , are you generalizing across all calibers. I have shot 22, 22mag, 9mm, 38, 357 and 45acp hollow points in cold weather using a multitude of manufacturers and have never had any weather related issues. I have seen problems with different manufacturers, usually across specific lots. I'm curious to hear if anyone has run into weather related issues. I will also add that none of my practice shooting was done below 20 degrees if that makes a difference.