In my experiance temp. never effected whether or not the plant hermied. I am an outdoor veteran and have dealt with 100 degree heat-no hermies. Plant stress and genetics are the main factors.
The sex of a Cannabis plant is not determined at conception, unlike animals. The sex of the plant is determined partialy by genes and partially by the environment. A stressful environment will predispose the plant to male and a low stress environment will produce more females.
What about hermis? When the sexual expression is effected by the environment, some will stress to the point of hermaphrodite. Genes play a roll too, the more inbred plants are more likely to produce hermis.
Cannabis tolerates high tempetures easily as long as there is enough available water. Plants stressed to the point of wilting are no more likely to hermi then unstressed plants, in my experience.
i would think that no matter the temp, there isn't trapped air on the plant if it is outside. it gets regular CO2 as well as (hopefully) a good H2O source and at least some air flow (even on the most sultry of days). that would probably be be helpful. at the same time you ask you question, you could ask this... why is it that the tiniest light leak indoors can cause a hermie, but a big, bright full moon outdoors won't?