Short answer is YES, your iPhone will work in the jungle humidity
I thought twice about taking my iPhone to Peru or the Amazon jungle, for theft risk and humidity reasons. But definitely glad I did. It worked fine in Peru’s Amazon jungle in September 2015 (end of the dry season).
Great for staying in touch, trip advisor research, photos, video clips and took a nice little time lapse of sunrise over the Amazon river when we got up at 4:30am to go to the parrot lookout hut, next to the claylicks where they arrive every morning around 6am to feed.
Here’s the time lapse video clip