Amegakure, the rain village used to be an industrialized village located somewhere between the three of the five Shinbo countries. The cantankerous Ame ninjas were often employed for assassination missions, an in-demand expertise, which was highly valued. As the name suggests, it rained cats and dogs in Amegakure. All the water from the rain ended up in a lake.
Sources : https://accountsupport697459633.wordpress.com/2020/08/10/boruto-the-terrifying-fate-of-the-rain-village/