The hypothetical reach of a nuclear detonation over Washington, D.C., depends entirely on the weapon’s explosive power and the environmental conditions at the time of the blast. The answer to “how far” is not a single distance, but a series of expanding radii, each defining a different type of devastating effect. These effects range from immediate physical destruction caused by the blast wave and intense heat to delayed contamination from radioactive fallout. An analysis requires establishing the characteristics of the weapon used, as modern nuclear arsenals favor smaller, more numerous warheads rather than the multi-megaton devices of the Cold War.
Defining the Explosive Power
The weapon’s yield, measured in kilotons (kt) or megatons (Mt) of TNT equivalent, is the primary factor determining its reach. A kiloton is one thousand tons of TNT equivalent, and a megaton is one million tons. Modern strategic warheads typically fall into the range of 100 to 500 kilotons, vastly more powerful than the 15-kiloton bomb used on Hiroshima. A 500-kiloton strategic warhead projects damaging forces over a much larger metropolitan area than a smaller tactical weapon.
This destructive power is distributed across three primary mechanisms: blast, thermal radiation, and nuclear radiation. The height of the detonation also dictates the outcome. An air burst maximizes the blast and thermal effects, covering a wider area with less localized fallout. Conversely, a ground burst, where the fireball touches the surface, creates massive radioactive debris, maximizing the reach of long-term contamination.
Immediate Physical Destruction Radii
The immediate physical effects of the blast—the shockwave and the intense heat—create distinct zones of destruction radiating outward from ground zero. Using a hypothetical 300-kiloton warhead detonated high enough to maximize the blast effect over the National Mall, the initial destruction would encompass most of the District and its immediate suburbs.
Zone 1: Total Vaporization and Extreme Damage
Within a radius of approximately 0.6 miles (1 kilometer) of the detonation point, the blast generates an overpressure exceeding 20 pounds per square inch (psi). This leads to the near-total destruction of all above-ground structures. Within this inner zone, the fireball’s intense heat vaporizes or carbonizes everything, including the U.S. Capitol, the White House, and the Supreme Court. The blast wave moves outward from this center, carrying wind speeds of several hundred miles per hour.
Zone 2: Severe Structural Damage
The severe damage zone would extend to a radius of roughly 2.5 miles (4 kilometers). In this area, residential structures are almost completely destroyed and major concrete buildings are structurally compromised. This zone would cover Arlington, Virginia, including the Pentagon, and reach into parts of Northern Virginia and Southern Maryland, such as Crystal City and portions of Alexandria. The blast overpressure in this ring, at around 5 psi, is sufficient to collapse most typical wood-frame homes and shatter internal organs.
Zone 3: Thermal Radiation Reach
The reach of thermal radiation, which accounts for about 35% of the weapon’s total energy, often extends far beyond the blast radius. For a 300-kiloton airburst, unprotected skin exposed to the flash would suffer third-degree burns out to a radius of about 5.5 miles (9 kilometers). This distance encompasses a significant portion of the Washington metropolitan area, including Bethesda, Maryland, and Falls Church, Virginia. The heat pulse is intense enough to ignite widespread fires in flammable materials, potentially leading to a massive firestorm across the wider region.
The Wider Reach of Radioactive Contamination
Radioactive contamination, or fallout, represents the secondary reach of the event, governed by atmospheric conditions rather than blast physics. Fallout consists of particulate matter, vaporized soil, and weapon residue sucked up into the mushroom cloud, which then drifts downwind. Unlike the instantaneous blast, the fallout plume can travel for hundreds of miles.
The wind speed and direction at various altitudes are the sole determinants of the contamination footprint. If prevailing winds are from the northwest, the fallout would be carried southeast, potentially contaminating Southern Maryland and the Chesapeake Bay. If the wind is from the southwest, the fallout cloud could travel northeast, placing major metropolitan areas like Baltimore and Philadelphia in its path.
A ground-burst detonation maximizes fallout and can result in dangerous dose rates extending a hundred miles or more downwind within the first 48 hours. The dose rate defines the level of radiation exposure. Simulations show that a ground burst in D.C. could spread lethal levels of fallout over large parts of Maryland, Delaware, and Pennsylvania. The dangerous radiation can create a long, narrow exclusion zone stretching up to 200 miles from ground zero, making the long-term geographical reach far greater than the immediate physical damage.