North Korea's nuclear tests haven't been that big. Though the last one was much bigger than the first two (20-30 kt), which were Hiroshima sized. By WWIII standards the first ones were all tactical nukes.
And that's assuming the bombs work properly, and don't fizzle (giving a smaller yield).
But they're not going to destroy whole cities in one go. They might kill most people within a 1 mile radius say, but outside that distance being in shelter is likely going to save you. Plus if you're further away, avoiding fallout is a really good idea.
Also, North Korea's missiles are pretty shitty, and not accurate enough to aim at specific targets - like cities. So it would have to be blind luck to get a hit - but a successful launch would still cause fallout. And being indoors is going to help with that.
Biting the hand that feeds IT
