18 inches took some places in my area up to a month to even dry out from with Milton. Some rivers rose for a long time after the storm. Then it took awhile to come down. There was one place, maybe around a lake, where I think some homes couldn't be accessed for a month due to water still being too high. That was on the local news within last week or two. So it was a month they went. And some of these places have had water pumped out too. It's flat here, so it takes a lot longer to get rid of the water.
I can't imagine devastation from a few feet of rain, let alone anything close to what they might have gotten and having it come down in elevated terrain.