Imo, the northeast has the atlantic ocean air, plus being more humid. Add all the salt, and deicing chemicals on the roads during winter, and your guaranteed rust. Even aluminum looks terrible after 5 years out in the weather here.
My brother who lives a few hundred yards from the ocean's shoreline here has a small tool shed that was built 2 years ago in the rear of his home. They used iron screws for the door hinges....says those screws are so rusted now he can barely remove them so he can replace them with stainless ones.
Even the unprotected steel portions of the front differential on my tacoma are showing a thick surface rust that I never bothered to cosmoline it. Rest of the truck looks amazingly good after 6 years being outside 24/7.