Ambient temperature really doesn't matter. I mean it does, but a pack is going to cook without cooling whether it's 30 or 90F outside. It will just happen a little slower at 30.
It's a good thing the Insight doesn't use NiCd batteries. The car would probably almost need to be scrapped, if not completely stripped down and cleaned. Cadmium is really nasty stuff, and is prevalent in the electrolyte of NiCd batteries.
I don't believe there is any real toxicity risk with NiMH batteries.. not that the metal hydrides are going to be good for you, but they're not nearly as toxic as something like cadmium, and I don't believe they diffuse into the electrolyte like cadmium does in a NiCd battery.
Still, proceed with catution... This sounds messier than I had imagined. Each cell can produce several drops of fluid in a single, short venting event.. This event almost certainly caused complete venting of the electrolyte.. which causes separator dry out.. which causes cell shorting, and more heat.. etc. You managed to send your pack truly into thermal runaway! Congrats
This also explains why your paralleled pack is dead(14V). It discharged itself through the shorted cells, which certainly contributed to the problem..
You need to be careful with that one too. It probably stayed cool because of the fan running, but extended reverse discharge even at low rates will vent cells every single time, if left long enough. The cells will just kinda dribble electrolyte. It's also quite possible that it wasn't a low rate event.
I'm sorry to say, it seems likely both packs are toast.
It would be interesting to weigh the cooked pack and see how much water it lost.
Oh, and PICS!