There will be a fire: a vast, world-consuming fire, brought on by the judgment of the gods. It's coming whether you want it to or not, no matter what you do or do not do, regardless of your good intent or lack of same.
You can build all the shelters you want. You can burrow underground to your heart's content. What you don't understand, what you've never understood, is that when the world burns, the forests will grow back — slowly, cautiously, first shoots poking up out of the ashes like a soldier in a shell-hole — but the cities never will.