It’s Florida. It’s Florida residents. It’s surviving fantasy Florida
Ok, you just said 3 sentences. 1st was a setting, 2nd was a character, 3rd finally was actually a premise.
That said, it only barely qualifies as a premise. It's incredibly shallow. What about fantasy Florida is a threat that this guy has to survive? I could survive just fine in IRL Florida, and just adding rain doesn't add any kind of threat. In fact, a little rain in Florida would make it easier to live there if anything by bringing down the average temperature.
That said, even fleshing out the threat is not adding anything to the premise. That would be adding to the setting.
Let's use "The Last Of Us" as an example. What's the premise of "The Last Of Us?" If you said surviving the zombie apocalypse, you would be dead wrong. The zombie apocalypse was the setting in that game. The premise was getting a girl who's immune to zombification through the zombie infested lands to a safe secure facility so she can be researched for a potential zombie vaccine.
So, if your question is whether or not "surviving fantasy Florida" is a good premise, the answer would be "no." Just like surviving the zombie apocalypse is not a good premise. Even the earliest zombie movies, like "Night of the Living Dead," didn't have simple survival as the premise. Yes, "Night of the Living Dead" had survival as a core aspect of it's premise, but it's actual premise had a little more to it. It was surviving the zombie apocalypse with a disparate group of people stuck together in a house. In this case, the way the different personalities played off of each other was a huge part of what made the premise work.
You really need to add more to it in order to make it work. You need to have some sort of objective.
What's your Florida man trying to do in "Fantasy Florida?" Is he trying to reunite with a family member? Is he trying to raise a child he found orphaned in the hellish land? Is he looking for lost treasure? What's he doing?