Yeah, it's just their way of getting you to cough up enough money for another phone, if you come in with a problem, they'll check those sensors, and if they are red, they'll say, "you've been exposed to water, that's what this is happening, the warranty is voided, etc. etc." so at that point youre screwed haha
Here's a thread that discusses the sensor. There are other mentions in other threads. I also remember one thread that posted close-up pics taken with a good camera setup.
Here is a brief YouTube clip showing how to locate the headphone sensor with 3 stills at the end that show the sensor better.
As to your concern, I'm inclined to think that humidity alone would NOT be enough to trigger the sensors. Why not contact an Apple Genius at a nearby store since they should certainly know about that living in the same region.
Tyler: I don't think that humidity will cause any extensive problems. I live in a humid area and haven't heard of anyone having any problems. I'm more worried about leaving it in the hot car compared to humidity.
Yeah, idk what i'm going to do for 7th hour p.e. for baseball, i can't leave it in the locker room, people will stomp it, and the car issue, i just don't know, but i think itll be fine in the winter at lease haha