Frequently asked questions
Is Fallout Weather an emergency alert system?
No. It is an educational tool that describes the weather. It does not know whether anything has happened, it sends no alerts, and it is not official guidance. In a real emergency, follow instructions from authorities.
Where does the list of potential targets come from?
It is an illustrative list compiled from public sources: the three US missile fields, other strategic military sites such as bomber and submarine bases, and the largest metro areas. It is not a prediction of what would be attacked, and no one outside government knows what a real attack would look like.
Why does the map change from day to day?
Fallout is carried by the wind, and the wind changes. A target that would send fallout over you today may send it somewhere else tomorrow. The 48-hour strip on the map shows how the picture shifts as weather systems pass.
Why is the wind on the ground different from the fallout direction?
A nuclear cloud rises several miles. Fallout then drifts down through every layer of air on the way, and the winds higher up are usually much stronger than the wind at the surface and often blow from a different direction. The wind you feel outside is a poor guide to where fallout would go.
What factors does the map take into account?
Many factors affect where fallout travels and how dangerous it is. This educational tool takes only three into account: the forecast winds from the ground up to the top of the mushroom cloud, an assumed weapon size, and an assumed burst type (on the ground or in the air). It does not account for the weapons actually used, radiation dose, the hotspots that rain and snow create, terrain and local weather, the range of particle sizes, or errors in the weather forecast. Treat the paths as a rough guide to what is likely, not a prediction.
If a path misses me on the map, am I safe?
Not necessarily. The paths are estimates from a weather forecast and a simple model. Real fallout patterns are irregular, and rain or snow can bring fallout down in places a dry-weather path would miss. Treat the map as a guide to what is likely, not a guarantee.
How far can fallout travel?
From a single ground burst, significant fallout typically extends tens of miles to a few hundred miles downwind, depending on the size of the weapon and the wind speed. Many ground bursts in one area, as an attack on a missile field would involve, would spread heavy fallout considerably further.
How long is fallout dangerous?
Fallout is most dangerous in the first hours and loses strength quickly. A common rule of thumb is that for every sevenfold increase in time after the explosion, the radiation dose rate falls about tenfold: after 7 hours it is about a tenth of the 1-hour level, and after two days about a hundredth. Official guidance is to stay sheltered for at least 24 hours unless authorities say otherwise.
What difference does rain make?
Rain or snow falling through a fallout cloud washes radioactive particles to the ground, creating concentrated hotspots that can be well away from the dry-weather path. The map flags precipitation for that reason.
Does it work outside the United States?
Not yet. The target list and place search currently cover the 50 states and Puerto Rico.
What information does the site collect about me?
The site has no accounts and keeps no database of visitors. The location you enter is sent to the weather service, Open-Meteo, either directly from your browser or through the server for this site, to fetch a forecast. Map images are loaded from OpenStreetMap, which can see the area you view. Our hosting provider, Google, logs IP addresses as any web host does. Your last location is remembered only in your own browser. The Privacy Policy linked at the foot of every page has the details.