I would NOT hold a snake for the drive. No disrespect toward Mel, but that's an accident waiting to happen.

BEST thing for your snake is to bag it (inside-out pillowcase works great) and tie it securely, then put it in a padded and insulated box. Then make sure the box is secure so that it won't go flying in the case of a fast emergency stop. Keeping the car warm should be fine...just use some common sense and make sure the travel-box isn't on the floor directly in front of a heat vent where it may get too hot.