Methodology

To find how a nuclear detonation could affect the 25 largest U.S. metropolitan areas (by population), 24/7 Wall St. used Nukemap, a site that simulates detonation of nuclear bombs. We have chosen two typical warhead yields, 100 kilotons and 800 kilotons, detonated in the air over the center of these cities. Metropolitan areas are ordered by total population, from smaller to larger. 

• Nuclear bombs with 100-kiloton yield detonated in the air at 0.9 miles altitude have a fireball radius of 0.24 miles and a light blast damage radius of 5.7 miles, for a total affected area of 102.3 square miles.
• Nuclear bombs with 800-kiloton yield detonated in the air at 1.8 miles altitude have a fireball radius of 0.55 miles and a light blast damage radius of 11.4 miles, for a total affected area of 409.3 sq. miles.

We also added the average population within the light damage blast range averaged over a 24-hour period. Light damage can be caused by an overpressure – the pressure caused by a shock wave exceeding normal atmospheric pressure – of 1 psi. (Psi is a measure of pressure equaling a pound of force per square inch.) All data is from Nukemap, except for metropolitan areas population figures, which come from the U.S. Census Bureau and are five-year estimates for 2020.