Great Advice from FEMA with help from the CDC. Sometimes it seems like we're all living in an onion.com simulation:
From the Fed's Website Ready.gov
Nuclear Explosion
Nuclear explosions can cause significant damage and casualties from blast, heat, and radiation but you can keep your family safe by knowing what to do and being prepared if it occurs.......
A nuclear explosion may occur with or without a few minutes warning.......
Fallout is most dangerous in the first few hours after the detonation when it is giving off the highest levels of radiation. It takes time for fallout to arrive back to ground level, often more than 15 minutes for areas outside of the immediate blast damage zones. This is enough time for you to be able to prevent significant radiation exposure by following these simple steps:
GET INSIDE
Get inside the nearest building to avoid radiation. Brick or concrete are best.
Remove contaminated clothing and wipe off or wash unprotected skin if you were outside after the fallout arrived. Hand sanitizer does not protect against fall out. Avoid touching your eyes, nose, and mouth, if possible. Do not use disinfectant wipes on your skin.
Go to the basement or middle of the building. Stay away from the outer walls and roof. Try to maintain a distance of at least six feet between yourself and people who are not part of your household. If possible, wear a mask if you’re sheltering with people who are not a part of your household. Children under two years old, people who have trouble breathing, and those who are unable to remove masks on their own should not wear them.
Ready.gov