In Zone II, there will be immediate intense thermal radiation (that can last for up to 30 seconds for a big H bomb), followed by a Shock wave.
STAY DOWN under your emergency shield, or cover, for at least A FEW MINUTES. Let the SHOCK WAVE pass over you. You will sense the Shock from the Noise and, possibly, three Pressure pulses (out - in - out).
Your emergency cover could be a ditch, a culvert, behind a stone wall, a basement, a building, your car, anything that will block the intense Thermal Radiation (not glass) and protect you from flying debris.
Survival Step 2: The first few minutes. DUCK - STAY DOWN. Let the Shock wave pass.