Hey Paul,
So your back in nice and cool Texas ...

I know extreme heat is bad. as extreme cold is bad. I would not leave it in the car, and would find some way to find a more suitable environment for your stuff.

I suppose if you have no choice, sunshades will help, and if you have a moon roof, open it slightly along with the windows. Park in the shade or a garage...do the best you can to keep the interior cool. All rather obvious, but other than that, maybe someone else has a suggestion