You shouldn't need supplemental heat unless you'll be cooling the car quite a bit with AC, in which case stop by WalMart and pick up a couple of hand warmers in the hunting section to put under the box, preferably wedged between the front and back seats on the floor and with a secure top. If it's a fairly small box, that may be good enough, but otherwise, put it in a snake bag or tied-up pillowcase before putting it in the box for security. Definitely do not transport in the tank. Good luck! My snakes just got moved a week ago to our new home.