When I think about the climate inside of old ranch houses back years ago, I’d say that everything in the house, sewing machines included, went through hot and cold temperatures on a regular basis. I remember when staying with my Grandma in the mountains of Colorado during the winter as a kid, of her stoking up the Warm Morning coal stove in the living room when we went to bed, and how cold the house was the next morning when we woke up. It went from hot with a banked-up stove at night, to colder than heck with a few glowing cinders by morning, every day, all winter long, every winter.
On the hot side, she didn’t even have indoor plumbing, much less air conditioning when it got hot in the summer. Whatever the outside temperature was, it was about the same in the house.
I don’t think hot and cold matter as much to sewing machine finishes as moisture does, but I could be wrong. I store my machines in non-climate-controlled areas here in Oklahoma, and haven’t noticed any problems with the finish crackling on any machines that weren’t already that way. I just make an effort to keep them dry.
And from my experience, having a piece of cloth under the presser foot to “protect the feed dogs”, or leaving a threaded bobbin or the upper tension threaded during storage will cause problems before hot or cold temperatures. The fabric and thread hold moisture from the air, and promote rust.
CD in Oklahoma