What If a Nuke Hit Seattle?

USA · Population 784,777 (2025, city proper)^{[1, 2]} · Density 3,608/km²

About Seattle

The largest city in the Pacific Northwest and a major US technology center.

Below are four scenario calculations using historical and modern nuclear weapons. Each row shows the radius of an effect zone in kilometers for an air burst at optimum height^{[3, 4]}. Radii are scaling-law estimates — see the methodology page for the underlying relations. Casualty and fallout estimates are not shown pending a verified population and fallout model.

Little Boy on Seattle (15 kt)

USA · 1945 · Hiroshima bomb

Effect zone	Radius (air burst)
Fireball	0.18 km
Severe blast (20 psi)	0.54 km
Moderate blast (5 psi)	1.54 km
Light blast (1 psi)	4.26 km
3rd-degree thermal burns	2.18 km
2nd-degree thermal burns	2.80 km

🎯 Run on Map More on Little Boy

W76 on Seattle (90 kt)

USA · 1978 · Common SLBM warhead (W76-0 from 1978; current W76-1 ~90 kt from 2008; W76-2 ~8 kt)

Effect zone	Radius (air burst)
Fireball	0.37 km
Severe blast (20 psi)	1.02 km
Moderate blast (5 psi)	2.80 km
Light blast (1 psi)	7.70 km
3rd-degree thermal burns	4.57 km
2nd-degree thermal burns	5.80 km

🎯 Run on Map More on W76

Castle Bravo on Seattle (15 Mt)

USA · 1954 · Most powerful US nuclear test

Effect zone	Radius (air burst)
Fireball	2.86 km
Severe blast (20 psi)	5.82 km
Moderate blast (5 psi)	15.4 km
Light blast (1 psi)	42.6 km
3rd-degree thermal burns	34.0 km
2nd-degree thermal burns	39.7 km

🎯 Run on Map More on Castle Bravo

Tsar Bomba on Seattle (50 Mt)

USSR · 1961 · Largest nuclear weapon ever tested

Effect zone	Radius (air burst)
Fireball	4.62 km
Severe blast (20 psi)	8.64 km
Moderate blast (5 psi)	23.1 km
Light blast (1 psi)	64.1 km
3rd-degree thermal burns	54.1 km
2nd-degree thermal burns	61.2 km

🎯 Run on Map More on Tsar Bomba

Limitations

These radii assume an idealized air burst at optimum height over the city center. The real extent of each effect depends on:

Burst height and whether the detonation is an air or surface burst
Terrain, building construction, and line of sight
Weather and atmospheric conditions
Distance from the detonation point within each zone

Casualty counts, fallout plumes, and radiation doses are not modeled on this page.

FAQ

What would happen if a nuclear bomb hit Seattle?

Seattle has a population of about 784,777 (2025, city proper) and an urban density around 3,608 per km². A Hiroshima-yield warhead (15 kt Little Boy), air-burst at optimum height, would produce a 5 psi moderate-blast radius of about 1.54 km — the zone in which typical homes and lightly built commercial buildings are destroyed. A modern strategic warhead (W76, 90 kt) would extend that moderate-damage zone to roughly 2.80 km, with 3rd-degree thermal burns reaching 4.57 km. Run the interactive simulator above to see the exact zones overlaid on the map.

What is the blast radius of a nuclear bomb over Seattle?

For a 100 kt strategic warhead air-burst over Seattle: fireball radius 0.37 km, severe blast (20 psi) 1.02 km, moderate blast (5 psi) 2.80 km, light blast (1 psi) 7.70 km, and 3rd-degree thermal burns 4.57 km. All radii assume an air burst at optimum height and scale with weapon yield.

How do different nuclear weapons compare over Seattle?

The 1 psi light-blast radius — roughly the limit of shattered windows and light injuries — runs about 4.26 km for a 15 kt Little Boy versus about 64.1 km for the 50 Mt Tsar Bomba. Blast radius scales roughly with the cube root of yield, so a 3,000× larger weapon extends the radius only about 14×.

Is Seattle a likely nuclear target?

This is an educational simulator and does not assess threat probability. Seattle is one of the world's most prominent cities in North America, which is why we feature it as a scenario. The purpose of these visualizations is to convey the physical scale of nuclear weapons — not to make any operational claim.

See also: full Weapons Database · Scientific methodology · Data sources.