Nuclear Explosion In A Blizzard

So working in one of the world’s greatest targets I get to wondering things. One over the past few days was “What would happen if a (terrorist / foreign power / supervillian / alien) exploded a nuclear device during the blizzard we just experienced? How much would the cold moisture contain or reduce the initial blast? Would the strong winds move fallout further or would the precipitation bring it to ground quicker? DCA shows about 1.5” of liquid precipitation equivalent.

Given that the region is already paralyzed by the weather event it would certainly be much harder to respond to the explosion, while at the same time your ‘audience’ (if you are someone who desires an audience like a terrorist) is already home and glued to the tv and internet anyway. I sometimes wonder if an enemy would be thinking along those lines.

Curious also about the different strength of explosions, from a few kilotons on up - how severely they are affected by the extreme weather event?


Off the top of my head.

A bunch of blowing snow is going to do a very good job of damping down the explosion. All that airborne ice is going to do darn good job of attenuating the spread of thermal and radiation effects of a bomb.

So, IMO the blast radius of “bad news” is going to lessen significantly.

On the flip side, all that ice turned into superheated steam is gonna make things WORSE close in.

Which is worse? A larger blast radius where people sorta die? Or a smaller blast radius where more people die percentage wise because they were parboiled?

A huge amount of snow in the air could reduce the thermal effects. Keep in mind this is entirely relative… You’re still going to be completely vaporized if you’re near the fireball, but someone several kilometers away would benefit.

Weather can also cause fallout to be concentrated. The irradiated clouds would drop more fallout on a smaller area, assuming the blast was small enough to be inside the troposphere. A megaton-plus bomb’s fireball will rise high enough that it will be above the weather.

On one hand I can’t help but feel that because, unlike high explosives, a nuclear bomb is, well, nuclear not chemical it will be less effected by things like air temp or density or moisture content. But on the other, the law of conservation of energy still applies. Some of the thermal, kinetic and radiation energy has to be used up more, or absorbed, by those factors.

But given the extreme levels we’re talking about, tens of millions of degrees, is the difference between warn weather and cold weather, or dry air or snow, really going to be a significant factor?

Long story short, it’s not going to make any real difference close to the explosion; it might dampen the effects of heat and concussion at farther distances. I think the main effect of snow/rain/fog would be increased scattering of the light from the explosion.

I’d be surprised if there weren’t studies from the '40s and '50s about the effect of weather on nuclear explosions.

Of course there are.

But they are in orange binders in safes and you need a security clearance to read them.

Here is one off the top of my head stat to think about.

Lets assume you are talking about a blizzard. And a mid sized household “yard”.

Lets call the yard 33 meters across (aka 100 feet). In a blizzard/heavy snow fall you can’t see across the yard.

That implies that any given line of sight from one side to the other is blocked by at least one and probably several snow flakes at any given moment.

That implies about a millimeter (give or take) of thickness of water along any given line of sight.

So a millimeter of water for a 33 meter yard. 30 millimeters for a 1000 meters (aka 1 kilometer). 300 millimeters of water for 10,000 meters (aka 10 kilometers aka about 7 miles).

If I was 10 kilometers from a nuclear blast, I’d be pretty happy that there was about 12 inches of water between me and the blast.

If snow keeps falling, then the fallout is going to be trapped in snow, which should be shoveled and hauled out before it melts. I remember from somewhere that the best thing to happen after a blast is lots of rain. That way, harmful substances will collect in low spots, or be channeled along the usual drainage pathways.

If the air is full of water in any form, it will absorb a lot of the thermal radiation (probably some ionizing radiation too). So that helps you avoid being burned to a crisp. The downside is that when water instantly absorbs a lot of heat, it turns into steam. Like what happens in an overheated pressure cooker, I would think the massive steam expansion would augment the force of the blast.

I think you’ve got it partly wrong there… the water means a smaller radius of thermal burns, but actually a stronger shockwave and blast radius (because water instantly superheated to a thousand degrees expands with a great deal of force).

Nonsense. Not only is the basic physics of nuclear explosion effects not classified, the Department of Defense and the Energy Research Development Agency (now the Department of Energy) published three editions of The Effects of Nuclear Weapons, a book that detailed the basic knowledge about nuclear weapons effects. Nuclear weapons aren’t some unique physical phenomenon. Like any explosion, it is conversion of heat into an outward expanding pressure wave compressed by traveling at the speed of sound. In the case of nuclear weapons, the source of energy is primarily X-rays (prompt radiation) which are rapidly absorbed by the atmosphere and converted into heat. This differs from chemical explosives where the energy is released as breaking chemical bonds and expressed as heating of the reaction products.

The immediate blast effects will not differ significantly with precipitation as the amount of heat locally overwhelms the density and moisture in the air and is converted to mechanical injury (the shock wave) regardless. However, the condensation cloud may occur more abruptly, providing some attenuation of the shock wave and likely significant attenuation of the thermal pulse. The amount and distribution of fallout primarily depends on the energy released by the weapon, altitude at detonation, and local height of the tropopause.


I doubt a blizzard would make the slightest noticeable difference. Ordinarily air contains plenty of water – it sits at about 50-80% relative humidity. Having a blizzard just means you’re at 100% RH, and given that this probably happened substantially via a lowering of the temperature (particularly at 5000’ or so where your nuke typically bursts), it suggests the total water content of the air hasn’t changed much at all. You just notice it, as a person, because it’s all in the form of fluffy white flakes instead of transparent water vapor. Certainly it takes more energy to turn snow to vapor than just heat water vapor, but given that the water content just isn’t that high a fraction of the air in the first place – I mean, you can breathe in a blizzard, after all – I’d be surprised if the total thermal inertia of the air changed much at all.

Well, yes and no.

Of course physics is physics. Atomic bombs are bombs. And regular bombs are bombs. And bullets are bullets.

And the U.S. military has done all kinds of studies on the effectiveness of such. Some measured. Some calculated. Some simulated. And some probably pulled out of someone’s ass for that matter.

And when the war gamers do their thing, they pull out these books that give them these magic numbers so they can play their game.

They don’t want the enemy to know those numbers. They don’t want to give the enemy free engineering and testing and all derived numbers.

Hence that stuff is generally classified.

Now if you or me or any other random dude on the internet wants to do a back of the envelope calculation based on first principles said results will not be classified (though at some level of sophistication I’d rather not test that principle).

But that brings up to why I posted the comment in the first place. Someone was complaining so to speak that such stuff wasn’t studied. Trust me, an atomic bomb in a snow storm has been studied to hell and back. But those results are most likely classified.

Which brings up back to back of the envelope first principles calculations.

Care to do a few and add to the discussion here?

Someone needs to do a simple calc. How much water vapor is in a given volume of air at like you say 100% relative humidity, vs how much EXTRA water is in a given volume when there is a blizzard.

Also, keep in mind that water is ice. Converting that ice to water before you can even heat it up a little bit more is a significant thing.

HMS is right that the super heated steam MIGHT make things worse. Again, calculations are required.

Something just occurred to me.

I can drive down the beach and lay out there all day. At some point the biggest damn hydrogen bomb within 4 light years will appear over the horizon. If I continue to lay out there for hours and hours I’ll get sunburned as hell and probably measureably increase my lifetime chances of getting skin cancer.

In a blizzard? Not so much.

Blizzards can help.


A proper Fermi problem and solution in two senses. Nice.

Again, take a look at the (linked) Effects of Nuclear Weapons, which discusses the estimated and observed results of nuclear weapons. (Although the last edition was published in 1977, we haven’t performed any above ground testing since well before then and thus, have no new pertinent observational data.) While this book was in publication it was widely available, and in fact, you could order it directly from the Government Printing Office or purchase it out of their stores. There is plenty of other research and information on nuclear weapon effects; check out the Federation of American Scientists archives, for instance. The one area of nuclear weapon effects on which there is still significant classified research are high altitude electromagnetic pulse (HEMP) effects, and the primary reason for that is that most of those assessments are based on models and tools that, while largely obsolete, are still themselves classified.

The details of specific weapon systems and especially protection/shielding systems are often classified, but the basic effects of the energy release are pretty much available to anyone with knowledge of heat transfer and atmospheric dynamics.

I haven’t performed a bunch of “back of the envelope first principles calculations” because the effect of a saturated atmosphere or precipitation will vary significantly with the size and altitude of the device, as well as the ground effects (in the case of a low altitude weapon). The distribution of fallout, for instance, will depend on the yield of the device, the altitude at which it is detonated, and the height of the tropopause at that point; if material is ejected into the stratosphere and be carried much further than if it is trapped in the troposphere. In the case of precipitation, it depends on the energetic yield and the absolute amount of water in the atmosphere. Obviously, the greater density of the atmosphere will reduce the acoustic shock, and the more water there is will absorb energy. How much attenuation this provides depends on a number of different parameters, so there is no “back of the envelope calculation” that gives some kind of overarching insight.

Comparing the effect of a blizzard in blocking constant sunlight (at a temperature of ~6,500 Kelvin at the upper atmosphere) to the effective temperature of a nuclear weapon (several tens of million Kelvin at the initial surface of the x-ray sphere for an instant) is like comparing apples to Eskimo; not only are they not the same thing, they don’t even have anything like comparable effects. The sun doesn’t create giant shockwaves or heat the lower atmosphere up to mass dissociation; a nuclear weapon doesn’t continue to radiate for an indefinite period. Sunlight typically doesn’t melt falling snow because the ambient conditions are too cold; the thermal pulse and blast wave would most certainly vaporize snow out to some distance which depends on yield.


Um, OK. bad billfish bad. I take it back. Although still a good Fermi problem.

Google tsar bomb. The size of the bomb is the only thing that matters. The bombs dropped on japan were firecrackers compared to what is possible.

Sick burn, bro.