Panic in Year Zero! (1962)

While on a fishing trip, Harry Baldwin (Ray Milland) and his family hear an immense explosion and realise the awful truth; Los Angeles has been leveled by a nuclear attack. Mayhem and madness are everywhere. Escaping to the hills with his family, he sets about the business of surviving in a world where, he knows, the old ideals of humanity will be its first casualties. Not one to give up, Harry does things to make sure his family has a chance at surviving.