Nope. Ya don’t. Figure at least ten to twelve feet of hot ash covering everything. No free flowing water for a couple of years. The sun blocked out. And so on and so on.
I don’t think it’s happening any time soon, but your best efforts to prep would leave you alone and very hungry in about a year.
We have snow in these mountains year round. All I have to do is dig below the ashline and filter what’s underneath.
I’ve been planning this since 9-11-01.
I’m trying to think how much different hot ash and no water would be to where I am living right now - Saudi Arabia? It might even be an improvement.