I think I accidentally made some cob weed on vacation last week, where it was hot as fuck. I have a fabric pouch that I keep my stash in when traveling, it's got 2 velcro closures, and the bag is lined with charcoal. Keeps 100% of the smell inside the bag.
Usually, I keep it in between my sunroof and the panel under the sunroof that slides open and closed to let light/air in. Generally it's only there for 45 minutes at a time, so I don't worry about the heat.
But while on vacation in a non friendly state, it was there a majority of the time, just baking away. After returning home, and getting my stash out to actually look at it, it has turned a dark golden color. I did notice when I smoked it, the smell was just insane. Like someone else said, my truck smelled like 30 hippies spent a few hours in there baking it out. I would roll a pinner, and burn half of it with the windows down, but the smell stuck like Chuck. Im not sure if it gained any potency, but it sure didn't lose any. Half a joint and I was completely baked.