I think all the risks stated above are correct. I have personally seen a lacquer finish cracked by cold temperatures in a car, and a soundboard cracked by dryness in a home.

But you might still want to take those risks depending on how valuable the guitar is, because the benefit of playing might outweigh the cost of a travel guitar or an inexpensive beater. I have a Martin Backpacker that I've taken camping in cold and wet weather, then played next to a hot campfire. I also loaned it to a friend who dropped it and cracked the soundboard. It still plays the same. If I were in your situation I would just take the basic precautions of leaving it in the trunk to avoid the most extreme heat and taking it inside overnight during any extreme weather.

The more conservative advice on this page definitely applies to any guitar of significant value. You should also consider the risk of theft, as a musical instrument left in view is a good invitation for a break-in.

I think all the risks stated above are correct. I have personally seen a lacquer finish cracked by cold temperatures in a car, and a soundboard cracked by dryness in a home.

But you might still want to take those risks depending on how valuable the guitar is, because the benefit of playing might outweigh the cost of a travel guitar or an inexpensive beater. I have a Martin Backpacker that I've taken camping in cold and wet weather, then played next to a hot campfire. I also loaned it to a friend who dropped it and cracked the soundboard. It still serves its purpose. If I were in your situation I would just take the basic precautions of leaving it in the trunk to avoid the most extreme heat and taking it inside overnight during any extreme weather.

The more conservative advice on this page definitely applies to any guitar of significant value. You should also consider the risk of theft, as a musical instrument left in view is a good invitation for a break-in.