What Would Happen If a Nuke Hit New York City?

The Short Answer

If a nuclear weapon hit New York City, what would happen depends on the weapon's yield, detonation altitude, and exact location. A modern strategic warhead — an 800-kiloton weapon, typical of those on Russian ICBMs or US Trident SLBMs — detonated as an airburst over Midtown Manhattan would kill an estimated 1.5 to 4 million people immediately and injure millions more. The blast would flatten most of Manhattan, spread lethal thermal radiation across all five boroughs, and generate radioactive fallout affecting the entire Northeast corridor.

This is not science fiction. These are the calculated effects based on well-established nuclear weapons physics, modeled by researchers like Alex Wellerstein (creator of NUKEMAP) and documented in the US government's own Effects of Nuclear Weapons reference.

The Scenario

For this analysis, we use a single 800-kiloton thermonuclear warhead — the approximate yield of a W76-2 or W88 warhead deployed on Trident II submarine-launched ballistic missiles, and comparable to warheads on Russian Yars and Topol-M ICBMs. The detonation is modeled as an airburst at optimal height (~2.9 km / 1.8 miles) over Midtown Manhattan, near the Empire State Building. An airburst maximizes the blast damage radius because the reflected shockwave merges with the direct wave to form a reinforced Mach stem.

Manhattan's daytime population density exceeds 70,000 people per square kilometer in Midtown, making it one of the most densely packed areas on Earth. The surrounding boroughs and Northern New Jersey add millions more within the blast and thermal radiation zones.

Blast Zones and Distances

The following table summarizes the major damage zones from an 800-kiloton airburst, based on NUKEMAP modeling and The Effects of Nuclear Weapons:

| Zone | Radius (km) | Radius (mi) | Overpressure (psi) | Effects | |---|---|---|---|---| | Fireball | 1.4 | 0.87 | — | Everything within the fireball is vaporized. Surface temperatures exceed 10 million degrees Celsius. All of Midtown Manhattan from Times Square to Grand Central is inside the fireball. | | Severe blast damage | 4.6 | 2.86 | 20+ psi | Reinforced concrete buildings are heavily damaged or destroyed. Fatality rate is effectively 100%. Covers all of Manhattan below Central Park and parts of Brooklyn, Queens, and Jersey City. | | Moderate blast damage | 7.9 | 4.91 | 5-20 psi | Most residential and commercial buildings collapse. Widespread fires ignite from ruptured gas lines and thermal effects. Extends into the Bronx, deeper Brooklyn, Hoboken, and Newark. Fatalities: 50-90%. | | Thermal radiation (3rd-degree burns) | 12.8 | 7.95 | — | Exposed skin receives third-degree burns. Clothing and flammable materials ignite spontaneously. Covers a zone from Yonkers to Staten Island. Anyone outdoors without shielding suffers lethal or severe burns. | | Light blast damage | 14.1 | 8.76 | 1-5 psi | Windows shatter, causing mass glass injuries. Light structures damaged. Extends to most of Long Island's western edge, Paterson, NJ, and parts of Westchester County. | | Thermal radiation (1st-degree burns) | 18+ | 11+ | — | First-degree burns on exposed skin. Temporary flash blindness for anyone looking toward the fireball up to 30+ km away on a clear day. |

Within the severe blast zone (4.6 km radius), virtually nothing survives. The overpressure of 20+ psi produces wind speeds exceeding 500 km/h (300 mph). Steel-framed skyscrapers are gutted; most are leveled entirely. Cars are thrown like debris. The Brooklyn Bridge, Manhattan Bridge, and all East River crossings within this zone are destroyed.

Immediate Casualties

NUKEMAP estimates for an 800-kiloton airburst over Manhattan:

• Fatalities (within 24 hours): approximately 1.5 to 2.5 million
• Injuries: approximately 2 to 4 million

These numbers account for blast effects, thermal radiation, and acute radiation exposure but do not include deaths from fallout, fires, infrastructure collapse, or the breakdown of medical systems. Accounting for those factors, total deaths in the first weeks could reach 4 million or more.

For comparison, the Hiroshima bomb was 15 kilotons. An 800-kiloton weapon is roughly 53 times more powerful. The blast radius scales with the cube root of yield, so the area of destruction is approximately 14 times larger than Hiroshima.

Radiation and Fallout

An airburst produces less local fallout than a ground burst, because the fireball does not touch the ground and does not loft irradiated soil into the atmosphere. However, an 800-kiloton airburst over Manhattan would still generate dangerous fallout from:

• Weapon residues: Fission products from the weapon itself
• Activated debris: Building materials, concrete dust, and other particles irradiated by the initial neutron flux and swept into the mushroom cloud
• Induced radioactivity: Neutron activation of materials within ~2 km of ground zero

The mushroom cloud would rise to approximately 20 km (65,000 feet) and spread northeast with prevailing winds. Within hours, radioactive particles would begin depositing across Long Island, Connecticut, and potentially Rhode Island and Massachusetts.

Fallout danger zones (assuming 15 mph winds to the northeast):

• Lethal fallout zone (> 300 rem in 48 hours): extends 30-80 km downwind, covering much of Long Island
• Dangerous fallout zone (100-300 rem): extends 100-150 km, reaching into Connecticut
• Advisory zone (10-100 rem): extends 200+ km, potentially reaching Boston

Anyone in the lethal zone without shelter would develop acute radiation syndrome within hours. Without medical treatment, the fatality rate above 300 rem approaches 50% and above 600 rem approaches 100%.

FEMA guidance states that adequate shelter — the center of a large concrete building, or a basement — can reduce fallout exposure by 90% or more. The critical window is the first 24-48 hours, after which radiation levels drop sharply.

Electromagnetic Pulse (EMP)

An 800-kiloton airburst at optimal altitude would produce a localized electromagnetic pulse disrupting electronics within the blast zone. However, the most devastating EMP scenario involves a high-altitude detonation (above 40 km), which can generate a continental-scale EMP affecting the entire eastern seaboard's power grid, communications, and digital infrastructure.

Even in the airburst scenario over Manhattan, the EMP would:

• Destroy electronics within the severe blast zone (where everything is already destroyed)
• Cause disruptions to unshielded electronics within 15-25 km
• Potentially damage portions of the regional power grid, complicating rescue and evacuation efforts far beyond the blast zone

The loss of communications infrastructure — cell towers, internet backbone, emergency radio systems — would compound the disaster by cutting off coordination between emergency responders and survivors.

Infrastructure Collapse

A nuclear detonation over Manhattan would trigger cascading infrastructure failures across the entire northeastern United States:

• Transportation: All bridges, tunnels, and subway lines in Manhattan destroyed. The Holland Tunnel and Lincoln Tunnel would be demolished. The NYC subway system — carrying 3.5 million riders daily — would be flooded and irradiated. Regional airports (JFK, LaGuardia, Newark) would be damaged or within fallout zones.

• Financial systems: The New York Stock Exchange, NASDAQ, Federal Reserve Bank of New York, and the banks headquartered in Lower Manhattan handle trillions of dollars in daily transactions. Their destruction would trigger a global financial crisis with no historical precedent.

• Utilities: Water supply from upstate reservoirs would be contaminated by fallout. The electrical grid across the tri-state area would collapse. Natural gas lines in the blast zone would fuel massive secondary fires lasting days.

• Medical capacity: NYC's major hospitals in Manhattan (NYU Langone, Mount Sinai, NewYork-Presbyterian) would be destroyed or severely damaged. The surviving hospitals in outer boroughs and New Jersey would be overwhelmed by millions of burn and trauma victims — far exceeding any medical surge capacity ever planned.

• Refugee crisis: An estimated 5-10 million people would attempt to evacuate the metropolitan area within the first 48 hours, creating the largest displacement event in American history.

Nuclear Winter Contribution

A single nuclear weapon on one city would not trigger nuclear winter. However, the firestorm resulting from an 800-kiloton detonation over Manhattan — with its dense concentration of high-rise buildings, fuel, and combustible materials — would inject an estimated 1-5 million tons of soot into the upper atmosphere.

In a scenario involving multiple nuclear detonations on multiple cities (a full-scale nuclear exchange), the cumulative soot injection would reach 150 million tons, blocking 70% of sunlight and dropping global temperatures by 8-10 degrees Celsius for a decade. Even a single city firestorm contributes meaningfully to this total and serves as a grim reminder that nuclear war's consequences extend far beyond the blast zones.

What To Do in a Nuclear Attack

According to FEMA's Planning Guidance for Response to a Nuclear Detonation:

1. Get inside immediately. Move to the nearest substantial building — concrete, brick, or underground. Do not stay in a car or a lightweight structure.

2. Get to the center of the building or the basement. Every layer of concrete and earth between you and the outside reduces radiation exposure. A basement offers a protection factor of 10-100x.

3. Stay inside for at least 24 hours. Fallout radiation drops by 80% within the first 24 hours (the "7-10 rule": for every 7-fold increase in time after detonation, radiation drops by a factor of 10). Going outside in the first hours is the single deadliest mistake survivors can make.

4. Remove contaminated clothing if exposed to fallout. Removing outer clothing eliminates ~90% of external contamination. Shower or wipe down exposed skin.

5. Monitor official communications. Use a battery-powered radio to listen for official guidance on evacuation routes and safe zones. Do not assume any direction is safe — fallout patterns depend on wind.

6. Do not look at the flash. A nuclear fireball can cause temporary or permanent blindness at distances of 20+ km. If you see a bright flash, turn away immediately and take cover.

The single most important factor in surviving a nuclear detonation outside the immediate blast zone is adequate shelter for the first 24-48 hours. FEMA estimates that proper sheltering could save hundreds of thousands of lives in a nuclear attack on a major city.