I've ran into a science journalism piece which reported on a NBER study fidning that lower human fertility following hot temperatures over 80 degrees Farhenheit. They attributed this effect to possible mediation by lower sex drive in higher temperatures, although other mediating biological effects leading to this decrease fertility were also mentioned
"Temperature extremes could affect coital frequency," researchers said. "It could affect hormone levels and sex drives. Alternatively, high temperatures may adversely affect reproductive health or semen quality on the male side, or ovulation on the female side."
Besides the obvious fact that temperature extremes would be unsuitable for any human activity, is there more direct evidence that subtle (as in a few degrees) temperature differences significantly affect sex drive in humans?