My personal experience was about a solo, three week stint two years ago in a situation beyond my control. I was parked on a brand new, black asphalt area with an electric hookup. It was August in Arkansas, so hot and humid.
Daytime temps were 100+. I recorded 102 air temp one day but measured 105-106 on the shady side of the asphalt area where the PUP was.
With PUGs and a tarp to try to provide a little afternoon shade on the main body of the PUP only, it would reach mid 80s inside the main compartment of the PUP. I closed the curtains to the bunk end I used just for storage so the A/C had less area to cool. This also made a little difference as I stuck my hand in there and it was quite a bit hotter.
It was bearable but not a chilly 72.
Getting off of that black top and finding some shade would have made a serious impact to the point that even at 102 degrees externally, I might have gotten down into the upper 70s, certainly low 80s. I have no quasi-scientific way to validate that, though.
And from the humidity perspective, I've had condensate run-off before. I've seen it many times, from a slow drip to a steady flow. That summer, it seemed I had placed a hose on top and turned it 1/3 on. It was phenomenal how much was coming off. It was a good thing I had previously made a "gutter" for the condensate, as it would have just dowsed my vinyl bunk ends and have algae growing on it in no time.