Krystal,
While you are in your car/truck driving to your destination, you will most likely have the heat or a.c. on during your drive. This should be enough climate control while you are driving (even at night if the temps outside drop you will most likely adjust the interior temps so you'll be comfortable).
It is when you stop for a break or if you decide to get a hotel room that you will need to be careful.
If your pit stops involve an area that is cold or cooler you will want to have some sort of heating element in the box. I would purchase at least one 40 hr heat pack for each box that your snakes will be in. While you are in the vehicle you shouldn't need to use them so keep them stored in a safe place away from your snakes at this time. However, when you stop you will want to affix one to the underside of the top of each box using strong tape.
If the climate is going to be warmer (generally if you need to turn on the air conditioner to cool down you can consider it "warmer"
then you will want to invest in some ice packs and do the same thing during your breaks. Just keep the ice packs in a cooler with plenty of ice (and a Coke or two) while you are driving. Also, keep your windows cracked to help dissipate excess heat build up in the car. A window visor (reflective or not - doesn't really matter) to help keep everything out of direct sunlight will also help.
If you are staying over night in a hotel room at some point then you should be fine with just bringing the box into the room with you. I always think that hotel rooms are excessively hot in the winter and cold in the summer so I, personally, would be likely to use a heat pack in the hotel room if I stayed in one.
A person's comfort zone is generally in the mid-seventies so if you are comfortable your snakes should be fine for a day or two at the same temperatures. Just don't feed them for at least a week before the trip and remember to soak/hydrate them at least one each 24 hours or so.
It sounds much more complicated than it is. Their temps won't be "ideal" during this period but there is no reason for you to drive in 80 degree weather with the heater on either.
-----
.
.
.
.
Stay United!

I'm still not sure if it's weird that my best friend is a two year old boa named Ronin. He's quiet, non-judgemental and listens... what more could you want?