MACBOOK

How did you figure the trunk would be 'better or worse' ~ than back seat for a portable computer?

The heat would accumulate over the course of a day's time; and could get above +150°F. easily.

Perhaps that'd get nearer boiling point of water! (And what about condensation/humidity?)

The best thing for Mac would be if someone took him on indoor vacation for a little AC + TLC.

Little else to advise in this matter -- except keep mac portable where it's neither hot, nor cold.

• Keep your Mac notebook within acceptable operating temperatures - Apple Support

https://support.apple.com/en-us/HT201640

PS: should the reference temperature be +60°F instead of +60°C please verify.

Either way, temperatures would be unverifiable; may not remain in safe zone.

And other perils could befall your mac buddy, too.

Good luck & happy trails!🌻