get a pet kennel, get a good snake bag.

Since I am assuming you are driving then your car will be climate controlled. All you need to do is line the kennel with soft towels to protect against sudden stops, and to absorb any waste liquid which issues from said snake. Then place snake in appropriate sized snake bag, a pillowcase can work as well, as long as you do not allow the snake too much room to move around in. Just enough to slither in a coil hither and yon. place snake in pet carrier and shut door. For bathroom stops: If the temperature is extremely hot, then just take carrier inside with you. I have done this, and no one says anything. Good luck!