I recently saw a comment chain about nuclear bombs, and that led me to thinking about this. Say there is a nuclear explosion in the downtown of my US city. I survive relatively fine, but obviously the main part of the city has been destroyed, while major zones extending from the center were also badly damaged. What would be a good response to (a) survive and (b) help out the recovery effort?
Move away from the mushroom cloud. It. Pay attention to the direction of the wind and try to see if the mushroom cloud itself is moving in order to tell what the wind is doing higher up.
You want to avoid being underneath it. That means primarily just moving away from it, adding more distance. But also, keeping in mind the top of that mushroom cloud is itself moving across the sky (being pushed by wind), so if it’s going the same direction as you, switch directions to get out from under it.
The mushroom cloud is full of radioactive material which will come settling out. If the initial blast didn’t kill you, this radiation is the next biggest danger. Just keep moving away, away, away.