Aloha, don't mean to derail the thread,
but I live in Ewa Beach on Oahu and it is hot pretty much year round. I won a Kala concert in a contest and decided just for grins that ukulele would live in my car full time.
It has been in the trunk four years now with no issues.
I AM NOT CONDONING THIS BEHAVIOR.
Just sharing my personal experience.
Carry on, good luck with the sale!