Guitar getting hot on car trip?

this is a real tuff question,
with no easy answer.

Wood does not like any extremes,
hot, cold, wet, dry

obviously, we can only protect them so much,
do as much as possible to shorten the "extremes".
air them out when possible, use light colored tarps, if possible,
when you open hot/cold cases, leave them closed a little while, if you bring them inside first, so thy warm/cool slowly.
(Cold guitars do NOT like quick temp changes, let them warm up IN the case for as long as possible, so the wood does heat up too fast,)


No guarantees
but guitars are meant to be played and used,

Good Luck