Living it the low desert I have shot a lot of Gold and Fuji Color 100 to 400, as a consumer grade films cold and Fuji color are not as temperamental to hotter temps than the professional films, negative and slide.
Hi, I'd say it's more likely the opposite - that the pro films are better able to withstand the heat.
I'm largely basing this on a test I oversaw way back when VPSIII was Kodak's professional portrait/wedding film, 1990s. Long story short, at the large US chain studio outfit where I worked we occasionally (rarely) saw a certain "artifact" that we presumed was "heat damage." (Yeah, we read the same industry literature that you probably did.) But we decided to investigate to find out how touchy our pro films were. I'm gonna sorta spell it out cuz it seems hard for people to believe.
FWIW we had both studios and traveling operations across the US, including in the desert southwest. So certainly we had a fair amount of film that would likely spend time in hot car trunks. I initially thought I could use my own car as a test bed, dark red color, daytime temperature around 95 F (~35C). But... it couldn't get near as hot as we wanted. So we rigged up a "hot box" with thermostatic control.
We figured that 140F (~60C) was probably a good place to start. This ought to hurt a pro color film pretty quickly, right? Here's the test plan: we'll keep unexposed film in the hot box, periodically pulling out samples. We'll use a sensitometer to make test exposures on the hot-box samples along with an always-refrigerated film sample as a "control." Test samples are all spliced together and run through a C-41 cine processor along with a "process control strip." Evaluation to be via tri-color density characteristic curves. From this we expect to be able to see exactly what happens as the film goes bad.
Once we have some concrete info we figure to have the photography departments issue some sort of advisory bulletin to their people, regarding just how touchy pro films are.
Oh, we decided to throw a couple of amateur films into the test, just to see "how much more rugged they are" compared to the pro films. I don't recall everything we tested, but it did include long-roll VPSIII in both 35mm perforated (acetate base?) and 70mm non-perf (estar base) as well as Kodak Gold 100 in conventional 35mm cassettes.
I've posted some of this info before, back when I still had actual test data. From that, roughly... NO FILM showed ANY sensitometric change until about 250 hours (that's over ten 24-hour days at 140F). At that point the AMATEUR FILMS started to go bad - the D-min (clear areas) began to darken and highest densities began to fall off (reduced contrast). The pro films, VPSIII, went about another 100 hours before any change was seen. Then they followed the same failure pattern.
As a note, once the films began to change they got progressively worse. But until the "failure point" was reached there was NO SENSITOMETRIC CHANGE in any of the films.
In the real world peak temperatures are probably only there when the sun is relatively high in the sky. So one could probably expect to at least double the "days" of my test. Ie, the pro film went around 350 hours/15 days in the test chamber; one might expect double that - a full month - in an actual hot car. I might add, if you could even get your car that hot. In my own car I don't think it went over 20F above ambient IN THE PLACES I WOULD KEEP FILM. Meaning on the floor or trunk, not in direct sunlight.
FWIW we never bothered issuing field memos through the photography departments. The pro films were so unexpectedly (to me, at least) rugged that we didn't think there was any need.
There's a lot more to the sort of related testing we did that suggests to me that Portra 160 is probably at least as rugged. But didn't repeat the hot box test.
