In a city, the fallout would settle on the roof of multistory buildings. People would only need to move down a few stories to be safe -- protected by several inches of concrete and steel. Even at Chernobyl, where firefighters were exposed to intense radiation, only about 31 out of 130 of them died.
Radiation hazards are usually hyped upward by assuming longterm health hazards and extrapolated by the unproven linear no-threshold theory.
The fallout also settles in the streets--and that means nobody leaves those buildings for almost a week. Also remember that the localized EMP will clobber the local power grid--no refrigeration. The ground shock fractures the water pipes--no firefighting capability, plus no drinking water. Most of the buildings in the lethal area will not have window glass, so external air will circulate into the buildings.
Blow the thing off at lunchtime, and you've got a million-plus people out in the open for the crud to land on.