91 is the temp I avg with Co2 burners going (propane) for the organic soil grows I do - towards the high end. I do end up watering more, but I have had great results thus far with no real loss to heat stress (unless I miss a watering day - but thats a whole other story). The theory that I run with is that these are late flowering summer plants grown in moderately high temps and arid conditions, so to bring out their best, align with what would be naturally found in the 'wild.' I believe stress due to heat (within reason) helps encourage resin development and can be a good thing for latter stages of flowering.