(CNN) -- Hawaii is taking those threats from North Korea seriously.
Starting Friday, the state will start monthly testing of a nuclear warning siren system aimed at alerting residents to an impending nuclear missile strike. It's the first such tests in the Aloha State since the end of the Cold War.
The test of the nuclear warning siren will be conducted during the monthly tests of the overall statewide warning siren system, according to the Hawaii Emergency Management Agency.
At 11:45 a.m. on the first business day of every month, a steady alert signal will blare from speakers for 50 seconds, followed by a 10-second pause and then a wailing "attack warning" signal for 50 seconds.
In the event of an actual attack, Hawaii's 1.4 million residents are expected to seek shelter immediately after hearing the attack warning signal. An emergency alert system will broadcast warnings on TV and radio as well.
'Not much time at all'
A fast warning is critical for the Hawaiian islands, which sit just 4,661 miles from North Korea. The state would only have about a 20-minute heads up before a missile launched by Kim Jong Un's regime hits the islands.
"Pacific Command would take about fives minutes to characterize a launch, where the missile is going, which means the population would have about 15 minutes to take shelter," said Vern Miyagi, administrator for Hawaii's Emergency Management Agency. "It's not much time at all. But it is enough time to give yourself a chance to survive."
On Tuesday, a top South Korean minister said the North may be able to pair a nuclear warhead with a long-range ballistic missile as early as 2018.
"They have been developing their nuclear capabilities faster than expected," Unification Minister Cho Myoung-gyon said Tuesday. "We cannot rule out the possibility of North Korea declaring the completion of their nuclear program next year."
Hawaii's emergency plan doesn't call for a mass relocation or evacuation of the islands, because there wouldn't be enough time with a 20-minute warning. Nor does the plan call for placing people in fallout shelters, because Hawaii's population has boomed since the 1980s so there are not enough shelters in the state to house everyone; whole neighborhoods are without even a single shelter.
In case of an actual nuclear strike, residents are instructed to go inside and remain sheltered for 14 days or until they are told it's safe to leave. While in shelter, residents should listen to local AM-FM radio stations for official information.
The emergency management agency estimates 18,000 Hawaiians would be killed during an initial nuclear missile attack.
A critical outpost
The attack warning siren test will be triggered from inside the 6-feet-thick concrete walls of a civil defense bunker nestled under the rock and dirt of the Diamond Head volcano crater, near Honolulu on the island of Oahu.
Turns out there are many perils in paradise. Normally, the people working around the clock inside are keeping their eyes on the many natural disasters that can strike Hawaii: hurricanes, tsunamis, earthquake activity in the region, volcanic activity or flooding. North Korea is now very much on the list of things to watch.
Hawaii is a critical outpost for the US military, hosting naval and air force bases. US Pacific Command, the military's headquarters for the Asia-Pacific region, is also on the island of Oahu.
While Hawaii is the first state in the US to prepare for a North Korean attack, it's not alone on the world stage. Japan implemented a similar alert system after four North Korean missiles landed off its northwest coast in March, one landing just over 100 miles from the city of Oga.