I took my centerfire rifle out today for the first time this year. Started with the same sight settings and load that I have been using for about 20 years. No hits on paper. I needed about -10 clicks of elevation to get his in the general area of where I was aiming. 
Checked the load, bullets and scope mounts, and then it occurred to me that the outside temperature was just over 40 Deg. I don't recall ever shooting in temperatures that cold before, could it be that the lower temperature caused a reduction in pressure or velocity that required additional elevation? Load was 16 gr. 4227.
Never had this happen before. 
Thanks!
Joe S

I've shot in the snow, when it was ~20° and was not far off my normal sight settings, at least not enough that I noticed it.

Joe,
I've had similar experiences as the others with the temp swings, usually not much change.  The only thing I've experienced with severe temp differentials is if you happen to be shooting in extreme sub-zero, some brands of primers can cause a delay.  In extreme heat, conditions, above a 110°F some powders don't play well.  I've experienced some changes but usually it's in a string.

Revisit your loads, lube, barrel conditions and settings.  Not saying you'd have those issues, but variations like what you described, if it was me and my equipment I'd hazard a guess and say I did something different.
Greg

Todd,
Made me chuckle, been there.
G

"Never will forget hearing kind of a zipper sound pulling a rifle out of a case at the range. Thought the front sight might have hung up pulling it out. Turned out to be the sound of a turret being spun at a high rate of speed."