STS,
Yes, patterns can be affected by temperature and humidity. No doubt that a frosty morning well below freezing isn't going to give as good a pattern as a nice 80* setting. But what's to be done about it? I try to keep things as apples to apples as I can and test my combinations in hunting like conditions best I can. Then you truly know what's gonna happen on that 21* snowy morning at 40 yards.
A factor not often recognized is the difference between a clean bore/choke and a dirty barrel. Patterns will begin to deteriorate at a certain point when the barrel/choke gets dirty enough. Clays shooters, bird hunters and small game shooters don't worry about a dirty bore too much. Those situations are pretty forgiving with clouds of small shot and 30" circles. Turkey and predator hunters that want to deliver a precise pattern at longer ranges on much smaller target areas should be more aware of how their gun shoots after 18+ shots fired. A dove hunter might not clean his barrel for the entire season with hundreds of shots fired. A predator hunter concerned with optimum performance probably should scrub the barrel and choke by the time he's fired 25 or so shots.
