Speaking for SE Florida here...
I've lived everywhere from the edge of the Everglades to out on one of the barrier islands, 2 blocks from the Intercoastal and 2 blocks from the beach, and I've never had a rust or corrosion issue.
That said, I'm not storing my guns out in the garage or the like, so their exposure is pretty limited to when I take them out and shoot or handle them, but even in conditioned homes I've had other non-firearm household items get a bit of rust here and there. Nothing on my guns, and I use Slip products exclusively.