What's the warning time on a nuclear strike in a modern country like America? How long would the average citizen have before the first nukes struck down?

Also, what's the best strategy to survive a nuclear strike given only hours to prepare? I'm concerned specifically with what sort of building to seek shelter in, whether to attempt evacuation of the city or to just find a sturdy building, and how to minimize the danger of nuclear fall-out

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    $\begingroup$ I have to say this: duck and cover! $\endgroup$
    – PatJ
    Commented Nov 9, 2016 at 5:40
  • $\begingroup$ Check out Homeland Securities website. https://www.ready.gov/nuclear-blast $\endgroup$
    – X_Wera
    Commented Nov 9, 2016 at 8:41
  • $\begingroup$ If you're going to tag with hard-science, you shouldn't use the science-based tag. The science-based tag is essentially the hard-science tag but without citations. $\endgroup$
    – Azuaron
    Commented Nov 9, 2016 at 16:33
  • $\begingroup$ Most of the answers seem to have neglected the obvious best strategy: don't live in a city, or near a military base. $\endgroup$
    – jamesqf
    Commented Nov 9, 2016 at 16:54

5 Answers 5


The tag usually calls for equations. Since you are asking about real-world engineering, I'll answer with these "hard data" points:

  • A country near the enemy might literally have only a few minutes. That's why Kennedy was so concerned about Soviet nukes in Cuba.
  • A similar effect can be reached with missile submarines, especially if they launch at less than maximum range (link to a paper on depressed trajectory launches).
  • The time for an ICBM traveling from the Soviet Union to the US would be around half an hour. Regarding Cort's answer, Clinton was right that a president has much less than 30 minutes to decide -- first the Air Force makes sure of their detection, then the order is deliberated very briefly, then the order must be implemented. This paper has the 1979 incident on p. 4.

If you really do have hours, run!


The answer to this varies immensely. On one hand, you have Hillary Clinton claiming there may be 4 minutes between a president deciding nukes need to be fired and a retaliatory strike. While the authenticity of this number is debated, it does suggest the timelines which our nation responds on. This suggests that they feel there are reasonable scenarios where this response time is in-kind with the intel they get. It goes without saying that the average citizen will not be given intel as it comes, so their warning will come noticeably after the government response. It would not be unreasonable to assume that your warning, as an average citizen, consists of a very bright warning flash followed by a very loud warning sound.

On the other hand, we have the Doomsday Clock, which is intended to be a general sense of how close we are to nuclear war. You could argue this is a warning of nuclear strikes that has been given since 1947, so in that sense, your citizens are receiving years worth of warning.

Somewhere in this range is the answer you are looking for. The actual answer varies immensely based on many factors not included in your answer, and many of which cannot be answered using publicly available documents.

Survival techniques vary as well. The proper response to a "rogue nation" lobbing one or two nuclear devices at the Western nations is very different from the response for Russia deciding that it's time to unleash their arsenal. The latter comes with substantial risk of nuclear winter, so survival techniques are very different.

  • $\begingroup$ Remember that the decision time for the president (or his successors...) is much shorter than the actual time between launch and detonation. It takes time to detect the launch, verify that it is an attack, notify people up the chain of command, and reach the NCA. Then it takes more time for the NCAs orders to trickle back down to the forces that will have to retaliate (and to civil defence who will notify the general population, that is you, the person wanting to survive). $\endgroup$
    – jwenting
    Commented Nov 10, 2016 at 7:26
  • $\begingroup$ @jwenting Agreed there is more to it. Hillary does claim that he timer is not just the decision time, but the time from decision to action ("There’s about four minutes between the order being given and the people responsible for launching nuclear weapons to do so.") In this case, the OP is talking about hours, so knowing that this part of the story is measured in single digit minutes does frame the story quite well. And you can be 100% without-a-doubt-proof-positive-be-certain that notifying the general public is not their primary concern during those minutes. $\endgroup$
    – Cort Ammon
    Commented Nov 10, 2016 at 15:13
  • $\begingroup$ in fact you may well decide deliberately to not notify the public, in order to prevent panic and routs that would make getting relief to the affected areas afterwards much harder and potentially cause more casualties in the surrounding areas from famine, riots, looting, etc.. It's a hard clinical decision to make, but probably the correct one if there's no time for an orderly evacuation. \ $\endgroup$
    – jwenting
    Commented Nov 11, 2016 at 6:50

For surviving a nuclear attack at a moderate distance, there are two basic rules:

  1. Put as much dense matter between yourself and the explosion as possible to minimize radiation poisoning
  2. Avoid getting crushed by falling rubble

For avoiding radiation, the best place to be is underground. Preferably in a bomb shelter obviously but even a regular basement can significantly improve your survival chances. If you can't reach an underground location quick enough, though, every little bit will help: Radiation spreads out from the blast in straight lines and is absorbed by all forms of matter, so get as much "stuff" between you and the bomb as you can. Heavy metals like lead are best but even regular walls and furniture are better than nothing. Water is also very good at absorbing radiation so jumping into a pool can help you if you happen to be next to a pool when you see the flash.

The infamous "duck and cover" advice is mainly about the second point, if you're close enough to the blast that the building you're in might collapse from the shockwave. This is similar to earthquake safety; hiding under a table can improve your chances for survival once all other considerations are met. Avoid windows, as these will shatter easily when the shockwave hits.

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    $\begingroup$ Prompt radiation -- the radiation from the explosion itself -- is negligible for anything from a Hiroshima-sized bomb upwards. If you are close enough to be affected, the thermal blast is a far more serious concern. (Prompt radiation effects don't scale that much with increased yield, while thermal blast does.) However, in order to survive the thermal blast, you'll want dense matter between you and the blast as well, so that guideline holds true. -- The radiation you need to worry about is the fallout. $\endgroup$
    – DevSolar
    Commented Nov 9, 2016 at 13:09
  • $\begingroup$ The other killer is blast overpressure, which could collapse your lungs and kill you even if you are shielded from the thermal pulse. $\endgroup$
    – Thucydides
    Commented Nov 10, 2016 at 6:16
  • $\begingroup$ @Thucydides Is there any way to defend against that though? I based my answer on the assumption that you are far away enough to survive by taking the right actions. $\endgroup$ Commented Nov 10, 2016 at 10:29
  • $\begingroup$ The best way to survive is to seal the bunker in such a fashion that the overpressure will not penetrate the enclosure. A set of shutters over the air intake and sealed door is a minimum, but the has to be scaled to the amount of overpressure being expected (if your shutters fail at a +5psi then you are hooped when they spring open at + 6 psi...) The threshold for lung damage begins at +15 psi. cdc.gov/niosh/docket/archive/pdfs/NIOSH-125/… $\endgroup$
    – Thucydides
    Commented Nov 10, 2016 at 19:14

The potential warning will depend entirely on the nature of the threat. In the case of escalating political tensions leading to a nuclear exchange there might be days or even weeks of build-up which could also include evacuations of likely targets and other practical preparations by the government.

At the other end of the scale there are conceivable scenarios where there may be no warning at all. For example if a device was smuggled into a city and detonated or if warning systems for incoming missiles failed for whatever reason. It is also possible that a conventional or terrorist-style attack could be used to cause confusion and disrupt normal communications and transportation.

In terms of survival there are several considerations

The direct effect of the blast

Clearly there will be a significant area where your chances of survival are virtually zero whatever you do. In this case you might as well try to get as far away as possible in whatever time you have. As you get further away from ground zero the decision to evacuate or hide becomes more of a balance. Obvious being further way is better but getting involved with hordes of other fleeing people has its own dangers and you may well end up in the open and not much further away.

There is also the risk of buildings collapsing so even if you survive the initial blast you could just end up trapped under rubble with little prospect of rescue. But in reality you will just have to make a snap decision on finding a building which looks reasonably solid.

In urban areas subways are probably not a bad choice. They offer good protection from the immediate effects and even if one entrance is blocked there is a chance of travelling along the tunnels to find a clear exit and alt least you are just trapped and not buried. There is also a good chance that these will be among the first locations tackled by rescue and relief efforts plus they may have at least some emergency power and supplies.


The explosion itself will produce an intense burst of radiation, most notably gamma rays which are both harmful and penetrating and the thermal flash. Here the best protection is to get as much mass between you and the explosion as possible.

A more long-term hazard is fallout which can include a variety of radioactive isotopes in the form of fine particles. These are most dangerous when absorbed by the body with the most immediate risk being breathing them in and later contamination of food and water. There are some medical treatments which can mitigate this at least in part, notably administering iodine to prevent the absorption of radioactive iodine isotopes.

Also basic hygiene measures like avoiding exposure to dust, showering and using respiratory protection will help to some extent, not to mention staying inside.

Secondary Effects

There will likely be fires and extensive damage to power and water supplies and other infrastructure and in the immediate aftermath there are many of the same problems that you would find in a natural disaster. So clearly a high priority is the basic survival needs of food, water and sanitation.

Here a lot depends on the severity and scale of the attack as to how effectively the authorities will be able to respond. In the case of just a few detonations help may start to arrive withing hours, in the case of an all out attack you could be on your own for some time.

Here the top priority is to reduce your exposure to fallout so if possible change your clothes and wash at the first opportunity, the intention being to remove any radioactive particles stuck to your skin and clothing. Again the biggest radiation risk comes from inhaling or ingesting dust.


there is actually a ted talk about the last half of the question. https://www.ted.com/talks/irwin_redlener_warns_of_nuclear_terrorism?language=en


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