No need to duck and cover just yet. US intelligence officials are pretty sure North Korea can put a nuclear warhead on an intercontinental missile that could reach the United States, but experts aren't convinced the bomb could survive the flight.
They cite lingering questions about Kim Jong Un's nuclear know-how. Could North Korea deploy nuclear weapons successfully time after time and hit their targets?
Would its weapon system break apart from the heat and stress it would sustain as it re-enters the Earth's atmosphere at roughly 10 times faster than a speeding bullet?
"I don't think North Korea has a good measure of how accurate the missile is at this point," said Michael Elleman, an expert with the International Institute for Strategic Studies. "They don't know if the re-entry technologies will really hold up - whether the bomb will survive the trip."
North Korea has tested an intermediate one that could strike US territory Guam, as well as a longer-range missile that could reach Hawaii and perhaps the West Coast of the United States. The intermediate and long-range missiles are still being developed.
Kim must do more tests to master what is known as "re-entry" in missile parlance, experts believe. The process involves shielding a nuclear warhead from the high temperatures and force it faces when it re-enters the Earth's atmosphere at about 24,945km/h.
"In principle, Kim Jong Un could hit the United States with a nuclear weapon," said Elleman, a former scientist at Lockheed Martin's Research and Development Laboratory.
"In practice, I think they are probably a half-year to a full year away from having something that will work more often than it would fail."
Joseph Bermudez jnr, an internationally recognised expert on North Korean defence and intelligence affairs and ballistic missile development, agrees.
"Putting these things all together and making them work is extremely challenging, and they haven't yet demonstrated a capability to produce a reliable re-entry vehicle, which is what houses the actual nuclear device," he said. "Remember, they've only tested these systems very few times."
Still, Bermudez, said, North Korea is "on track" to figure it out.
US officials also think it's just a matter of time before Kim's programme fully matures.
National Intelligence Director Dan Coats told Congress in May that Kim has been photographed beside a nuclear warhead design and missile airframes to show that North Korea has warheads small enough to fit on a missile.
That same month, Lieutenant General Vincent Stewart, the Defence Intelligence Agency director, told politicians that it's only a "matter of enough trial and error to make [re-entry] work. They understand the physics, so it's just a matter of design."
For now, North Korean missile development is advancing amid extremely grave threats from Pyongyang and Washington.