They really thought everyone would just go down to the local schoolhouse basement, wait a week and everything would be back to normal.

I looked this up because I remembered reading that nuclear bombs don't have an excessively long fallout, since most of the energy is designed to be released during the detonation (as opposed to an accident like Chernobyl)

Sources say minimum of 24 hours, after levels fall significantly but you should still wait for direction. Another source said 3-5 weeks. Hmm.