Pyongyang's state-run KCNA news agency said on Thursday its army would complete plans in mid-August to fire four intermediate-range missiles over Japan to land near Guam as North Korea and the United States engaged in increasingly heated rhetoric this week over the North's nuclear weapons program.
While the governor of Guam shrugged off the North's missile warning and said there was no heightened threat, the government has issued a preparedness fact sheet.
In language that evoked the spectre of nuclear conflict during the Cold War, the guidelines cover what to do before, during and after a nuclear attack.
"Remove your clothing to keep radioactive material from spreading. Removing the outer layer of clothing can remove up to 90% of radioactive material," read the guidelines of what to do if caught outside.
"Fallout shelters do not need to be specifically constructed for protecting against fallout," it said. "They can be protected space, provided that the walls and roof are thick and dense enough (i.e. concrete) to absorb radiation given off by fallout particles."
It offers advice for parents who are away from their children during a strike.
"Stay where you are, even if you are separated from your family," it said. "Listen to the news. Do not call the school. Be patient. Wait for instructions to pick up your child."
Guam is home to about 163,000 people and a US military base that includes a submarine squadron, an air base and a Coast Guard group.
US President Donald Trump on Thursday warned North Korea against threatening Guam and said on Friday that the US military was "locked and loaded, should North Korea act unwisely."
"Though I don't want the temperature to get any higher, I think it's important also that there is clarity and that if there is an attack on any American soil including Guam, that it will be met with overwhelming response," Calvo told reporters on Friday. "I don't have any problem with that."