Rain radiation falls relatively quickly over time. Most areas become quite safe to travel and decontaminate after three to five weeks. Residual radiation is defined as radiation emitted more than one minute after detonation. If the fission explosion is an aerial blast, the residual radiation will mainly come from the debris of the weapon.
If the explosion occurs on or near the surface, soil, water and other materials in the neighborhood will be absorbed upwards by the rising cloud, causing early (local) and late (global) precipitous rainfall. Early precipitation settles on the ground for the first 24 hours; it can contaminate large areas and be an extreme and immediate biological hazard. Delayed precipitated rain, which arrives after the first day, consists of microscopic particles that are dispersed by prevailing winds and are deposited in low concentrations on possible large portions of the Earth's surface. Remove contaminated clothing and clean or wash unprotected skin if you were outside after the rain hit.
Hand sanitizer doesn't protect against falls. If possible, avoid touching your eyes, nose, and mouth. Do not use disinfectant wipes on your skin. That is, until one of them Googled the safety nuclear bomb how to shelter from the beach and found a Business Insider article titled If a nuclear bomb explodes, this is the most important thing you can do to survive.
Since large doses of radiation of approximately 20 roentgen or more (see radioactivity note) are needed to produce developmental defects, these effects would likely be limited to areas of heavy local rainfall in nuclear warring nations and would not become a global problem. A nuclear electromagnetic pulse (PEM) is the time-varying electromagnetic radiation that results from a nuclear explosion. Based on these estimates, the consequences of the more than 500 megatons of nuclear tests until 1970 will produce between 2 and 25 cases of genetic diseases per million live births in the next generation. The highest levels of outdoor rain radiation occur immediately after the arrival of rain and then decrease over time.
The 1963 Limited Nuclear-Test-Ban Treaty ended atmospheric testing for the United States, Great Britain and the Soviet Union, but two major non-signatories, France and China, continued nuclear testing at a rate of approximately 5 megatons per year.