I've played an acoustic guitar in freezing cold and blistering heat, and I did it for years--once it has been tuned, and the temperature doesn't dramatically change, it really doesn't make a bit of difference.

BTW: The absolute best musicians I've ever had the pleasure of meeting were members of the U.S. Naval Academy Band and the U.S. Army Band. They were the best of the best. Their skill level was such that it would be difficult for even some of the best concert musicians to comprehend. They do this stuff eight hours a day, every day of the week, and many perform under conditions that no one on this forum would even consider--regardless of the pay. No one, at least no on this forum that I've heard, including myself, is remotely close to being in their league.

Cheers,

Gary