Theres websites where you can play around and simulate the effects of various nuclear explosions across a map, such as
this one
One thing that suprises me about the simulation is the area of effect for 3rd degree burns - on the simulation I linked it is almost 25km radius for 3rd degree burns.
Fallout depends on height of the explosion, detonate close to the ground to maximise fallout, but then you lose the air blast radius.
So I think the thing to do would be to find a place where you won't be cooked by the heat, and which is as structurally sound as possible to withstand the air blast. Beyond that muster up your Mad Max education to survive
