Hey, I live in Florida, we have air conditioning down here. That keeps the indoor humidity at around 55% in the wet and sticky season, it's less in the cooler times. Besides, most speakers are impregnated with some sort of material which renders them impervious to moisture. I'd worry much more about speakers from areas with high ozone, that rots foam speaker surrounds faster. The surround is more likely to deteriorate than the cone in my experience.
