Guitar Abuse Central here... it was 33 degrees this morning... in our kitchen (old Farrm House, no heat).
This has been the norm lately with the Totally Stupid Arctic Air Mass that has drifted our way...
My Emerald X10N is on a guitar stand next to a gas fireplace. When I flip that on, it gets into the 60s fairly quickly and the X10N, of course, gets a lot more heat from one side.
Stays in tune.
Or very close, even with those goofy nylon strings.
In the summer, the X10 lives in an even more rustic area that can get over 110 degrees during the day and then drop back into the 60s-70s at night.
Again, no issues.
My GX stays outside most of the time and has gotten plenty of sun over the past 5 years or so.
My new Savoy... I'm a little more paranoid about that one. It is currently undergoing chill testing with the rest the instruments, but it stays inside its case when not being played.