After reading this thread, I feel compelled to bring to light a few things that might be less than obvious...
First off, not everybody lives in the sunbelt. So the heat, kids dying, etcetera doesn't always apply.
We don't all live (and park our vehicles) in the proverbial big city, and even if we did, often a car is as secure as an apartment, unfortunately. Where I work, we've got cameras all over the parking lots and campus police out in-force writing tickets for whatever they can get away with, and nobody gets broken into. My rural neighborhood, on the other hand, experiences a great deal of breaking and entering during the day when everyone's at work. I feel more secure keeping the instrument somewhat *with* me than leaving it at home (but not so much now that I have an alarm system at home).
The instrument will sweat when the temperature change is sudden, such as taking the case out of a hot car and opening it before it has had time to cool, or taking it from a cool place and opening it before it has warmed. That's when the finish-checking happens as well. Gentle changes in temperature are what you want to achieve, and obviously no extreme temps either direction if you can avoid it. We've got as many trees as we have parking spaces (it would seem at 8:05 am at least), so I can almost always park in the shade of a tree, if not the shade of a building (which I prefer).
Ever shipped your instrument by air? It's experienced temps of 20-below, farenheit. Shipped it by truck in the summer? 140 degrees and higher is quite probable.
Obviously, if you can avoid leaving any instrument in your vehicle for the better part of a day, then do it. If it has to happen though, and it does sometimes have to happen, then there are simple things you can do to keep your instrument happy and healthy in this frightful situation. It is important to keep the instrument case out of direct sunlight.
I care deeply about my Alembic. I will probably never again have the disposable resources to have another one built, so I take excellent care of it. There are times when it is A-Okay to leave it in the car/truck all day though, depending upon circumstances, and there are times when it is NOT A-Okay to do so. Just use common sense.
John (who wouldn't dream of leaving his Alembic in his truck on a day even remotely like today)
