Orange tabbies probably evolved past desert survival.

I took my boy with me on my three and a half day trek across country to our new home. I was in a 14 year old car that could barely make 35 when put to a hill. It was gruesome and we were equally terrified. He had free access to a kitty litter pan the entire trip and absolutely refused to use it, or eat or drink, while in the car. He was fine with using the kitty litter at hotels when we stopped. Like others have said, please be careful about the harness thing -- it seems unlikely that they'll go for the potty break thing and there are risks attached. Also be careful of the beds in the hotels, if your guys are the kind who crawl inside things -- some of them have areas in the back or underneath where they can, you know -- crawl inside. Put your do not disturb sign up the second you get in so no maid service or whatever opens the door while you are in a shower and lets a cat out.

Thanks for the followup - glad to hear you all made it!

Now that we're all safely here in Tucson, I thought I'd share what we ended up doing: Due to space constrictions, both cats ended up in their own carriers and stacked on top of each other (which I wasn't happy about, but it was pretty much unavoidable). Lined each carrier with a puppy pad. In the car, I was able to reach back and stick my fingers through the spaces in their carriers. We used the disposable litter pans (one for each night in a hotel and one for right after we got to the new apartment). Cranked the A/C. We left at about 8PM on the first and second days and drove for about 6 hours. Day two, stopped at a Super 8 in Tulsa. The cats started crying about halfway through the trip. First night in the hotel was a disaster (couldn't get the cats adequately settled, dad wanted them in the bathroom, cats cried in the bathroom to be let out, were let out and promptly started trying to scratch up the hotel beds, and so on). One of the cats missed the litter pan - we subsequently put the pans in the bath tubs and/or on top of a puppy pad. On our long day, we left Tulsa and drove to Las Cruces, NM. Stayed in a La Quinta, which was way better than the Super 8. Packed the cats up, each with a half-frozen bottle of water, and put a white towel over the top of the carriers, making sure to allow still for adequate ventilation. Checked them every time we stopped for gas, gave water a couple of times, which they didn't take. They drank a lot of water in the hotels, though. Thankfully, no accidents in the car. The third day was short, left in the morning to avoid the desert heat and set them up ASAP in the new apartment. Everybody's doing well, although they did run in terror from the giant drain roach in my shower - no predatory instincts whatsoever.

I moved three cats from Arizona to Oregon in August. My car did not have AC, so we drove at night. It was much, much cooler and no traffic at all! I also thought I could "rig a couple laundry baskets together" for the one feisty creature. Do not make the same mistake! By the end of the trip we had resorted to tying the broken pieces of plastic together with our shoelaces.

Be very careful with harness. I lost a favorite (formerly feral) kitty because I trusted a harness approved and fitted by the vet. The little bugger just turned himself inside out and left the harness dangling from the lead--never even pulled back on it. And this was after weeks of harness training and walkies to prepare him for an upcoming move! This happened in my in-laws' back yard. Although we never saw him again, and no one ever reported him via his chip, I often wonder if he's still around. For forty years, the in-laws were plagued by raccoons. The week after the cat got loose, there were no more dumped garbage cans or stolen cat food, and they haven't seen the raccoons since. Zeke was a terror.

Purely an anecdote, may not work with your cats if they are particularly active or curious, but when my mother drove our two (somewhat elderly) cats from Nebraska to Washington state, she was opened their cages and one alternated sleeping in her lap and on the dashboard, she put a towel up there after it initially climbed up. I'm sure this goes against all accepted cat-in-car safety rules, but it worked for them and the cats really enjoyed looking out the windows and being more in control of their movement and surroundings (they were never great closed in carriers because that just meant "we're going to the vet to get shots"). Obviously if it's hot, it's easy to overheat on a dashboard, too.

They did appreciate when I stuck my hand in the carriers and let them gnaw on it a little in revenge We gave ours a few http://www.royalcanin.ca/index.php/Veterinary-Exclusive-Nutrition/Feline-Nutrition/Medi-Treats, (to which their systems were already habituated). It was a decent way to distract them.

I'm considering trying to rig a couple of laundry baskets together and then putting them in that together with a small litter pan. Word of warning: I took my two chill cats on a three day road trip from New Mexico to Washington and even though they were on the seat next to me and I never saw them freaking out, they shredded the shit out of their carriers. Another day and they might have ripped them open. A laundry basket would NOT have survived that. Maybe a large dog crate (a catproofed one, for their toesies) would work better? My trip was through the desert in August, and my cats wouldn't eat, drink, or excrete until we got to the hotel, and my messing around with ice cubes and towels and treats just annoyed them. They did appreciate when I stuck my hand in the carriers and let them gnaw on it a little in revenge. They also hated hated hated Lady Gaga. But seriously, they'll probably be okay, even if they don't eat or drink for 6-8 hours at a time. Oh, and to spare me from eating all my meals in the car with them, I just took their carriers into restaurants with me. No one batted an eye, cats were air-conditioned, and I had company.

I should completely think through my response before I post, sorry! You can also freeze disposable diapers by themselves and use them as cooling pads. (I've used one on a sore knee.) Keep a cooler filled with ice (probably easier to find than a freezer for freezing cold packs), and periodically swap out a cool pad/diaper/cloth. FYI, in a heat-related emergency while on the road once, I bought a bag of ice and a towel, and laid the cat right on it. Seemed to work - the cat was none the worse for wear.