[amamnn]

Many factors could be involved. My grandfather used to say: "never load in summer to shoot in winter." There are benchrest shooters who only load their ammo on the day of the match, at the range. Such extremes are debatable and have not been definitely proven to be any help in ensuring accuracy. We do know a few things for sure. When the weather is colder the air is denser and your bullets will fly differently, especially in the lesser B.C. of the small bores. Allowing your rifle time to acclimate will help. Leaving it out in the car overnight before going to the range is a good idea if you trust it will not be stolen. Loading your ammo far in advance does seem to have an effect on accuracy as the seasons change, so you might not want to load in big batches. The load that was grouping well in August may need a tiny bit more powder or be seated differently in October. A rifle that was free floating in the warm weather may be touching the stock during some shots in colder weather. If you have not mastered breath control you may find a difference in cold weather. It could be a combination of these factors and others which I failed to remember just now. I've not had much trouble with accuracy as the seasons change, but all the above have been put forward as causes and cures of such accuracy problems by people who are supposed to know the business.