Hawaii reinstates Cold War-era nuclear attack warning signal amid North Korea tension The alarm has not been used since the Cold War.

 -- Hawaii is reinstating a statewide nuclear attack warning signal in December to prepare for a potential attack from North Korea.

The alarm, which has not been used since the Cold War, will be reinstated on Dec. 1 as part of a ballistic missile preparedness program, according to the Hawaii Emergency Management Agency (HI-EMA).

The agency instructed residents to immediately “Get inside, stay inside and stay tuned” if they hear the siren. Alerts will be sent to resident's phones and broadcast on television and radio. "When [HI-EMA] started this campaign, there were concerns we would scare the public. What we are putting out is information based on the best science that we have on what would happen if that weapon hit Honolulu or the assumed targets," said HI-EMA Administrator Vern Miyagi during an emergency preparedness presentation.

Since officials would have only 15 minutes or less of warning time before a North Korean missile's impact, Hawaii residents are advised to have a designated place to go for shelter. "There will be no time to call our loved ones, pick up our kids and find a designated shelter. We should all prepare and exercise a plan ahead of time so we can take some comfort in knowing what our loved ones are doing," said Miyagi in an interview with The Honolulu Star Advertiser.

Although the U.S. has conducted successful missile interception tests, there is no guarantee that the Navy would detect and intercept a target, the HI-EMA warns.

North Korean leader Kim Jong Un has not directly threatened Hawaii, but missile test launches over Japan and increased tension between his country and the United States prompted Hawaii officials to address the issue of preparedness.

An HI-EMA fact sheet explains that, based on the estimated yield of North Korean missiles, there could be anywhere from 50,000 to 120,000 burn casualties and nearly 18,000 fatalities if an attack occurs.

After an attack, residents would have to stay sheltered in place until the HI-EMA has fully assessed the radiation and fallout, which could take a few hours or as long as 14 days, the agency says on its website.

State officials have been holding town halls to answer questions from residents.

Hawaii currently has an alert warning for natural threats like hurricanes and tsunamis. Both signals will be tested on the first business day of each month.