You guys are way overthinking this shit.
Look at Haj who lives where its 110 out every day. Do you see him wearing stylish, athletic cut shit that matches the blanket on his camel and is made out of the same material that the Challenger space shuttle's failing O ring was made out of? Vents here, less material there, tighter in the crotch area so you can tactically thrust fuck yourself to death?
No. Motherfucker is wearing loose fitting clothing that covers most of his body made mostly out of cotton. Why? Because like we FINALLY figured out with the PCU system, you cannot keep heat/cold/water in or out of something forever. It's a matter of time before whatever space aged shit you have is compromised and then in most cases, it does a better job of retaining the shit you want on the outside once its on the inside.
Same goes for Haj and friends. Loose fitting clothing concedes the fact you're not going to keep the warmer air out unless you're in some Buck Rogers level enclosed space suit. You're not. So fucking forget about a AC temp guage on how cold you want your sack area to get. Secondly, and this is going to come as a fashion shock to our tight as fuck faggot pants wearing friends, but the more space between your actrual body and the clothing allows for that heat to move around and dissipate instead of turning your wrinkly ballsack area into a furnace that keeps getting stoked every fucking time you move and will only succeed in generating more heat and exponentially increasing the rate at which you get old man balls. Add that to designs where they either use non breathable materials and/or make certain areas with vents or thinner and you just have stupid fucking clothes on.
It's really that fucking simple.
I went shooting out in the desert yesterday afternoon. On my way there I pass a gym with an electronic board that has the time/date and temperature. When I passed it, it was 104 out. When I got to my shooting spot in the desert, my Kestrel said it was 107 in the shade. The ground out there which is mainly rock and sand was too hot to touch at times.
What did I wear?
Newer OCP top made for hotter weather with the sleeves rolled up a little and a thinner moisture wicking t shirt underneath. OCP pants with the kneepads (worth its weight in gold because of the rocks out there) where the pants were adjusted via the velcro and cinch system to be loose around my thighs and ankles and a sun hat. Was out there for 4 or so hours with next to no shade and was never hot.