Heat as from a thousand suns
When a nuclear weapon detonates incredible amounts of energy are released in the form of heat, blast, and ionizing radiation. The fireball that is created in the first minute after a nuclear detonation has temperatures as high as those on the sun, leading to intense thermal radiation that spreads in every direction with the speed of light. Therefore, everything that can be ignited within kilometers from the hypocenter ignites before the blast hits.
Within one kilometer (0.62 miles) from the explosion it is so hot that ceramic tiles melt, and at a distance of three kilometers paper ignites instantly from the heat radiation. It is not recommended to test out on your own skin by a fire how warm thermal radiation is when paper ignites. You will get seriously burned, with bad pain.
Within 1-1.5 kilometers from a nuclear explosion all biological material, including human beings, just evaporates instantly with nothing left. Bright silhouettes of humans left on the burnt pavements of Hiroshima were all that remained of people killed in this way. Within 2-10 kilometers from a nuclear explosion everyone affected will have the most serious third-degree burns on large parts of their bodies, with no chance of survival. Those who are fortunate enough to be more distant, but are hit by the thermal radiation, will mostly get second-degree burns, still unbearably painful and, in many cases, life threatening.
The sad experience from Hiroshima and Nagasaki tells us that in any city hit by a nuclear weapon there will be thousands of victims with serious burns from the initial thermal radiation in need of intensive medical treatment. In my country, Norway, with about five million inhabitants, we have only eight hospital beds at one specialized hospital designated to treat serious burns, which are luckily quite infrequent injuries under normal circumstances. In the entire USA there are only a few hundred such specialized hospital beds, which would be absolutely insufficient in case of only one nuclear explosion.
Therefore, when looking at burns only, there are no authorities or health care systems anywhere in the world that could offer adequate treatment to the victims of a nuclear weapons attack. Consequently, we, as doctors, prescribe prevention as the only possible way to hinder the immense human suffering we will face when nuclear weapons are used. The only prevention that is effective is to get rid of all nuclear weapons—the sooner the better.