Radioactive Fallout is a cloud of debris from a nuclear explosion, such as in the second Jericho episode. This fallout is super-heated, radioactive debris. Pulverized objects such as cars can literally fall out of the sky. If it is touched, it can cause third, second and first-degree burns. Fallout can also come in the form of rain, as it did in Jericho. That form is not as hot, just outside temperature. This rain can be of high acid content, depending on the severity of the blast, and what type of bomb it was. So, no matter what, seek shelter until you can confirm that the fallout is over. A fallout shelter is probably the best place to hide, but a regular, DUCT TAPED basement would be good as well.