I have spent some time gaming out how I would respond. There are very few scenarios where I think I'd try to leave my house, because I'd have to know the ground-level and aloft winds to a high certainty and/or see the plume of fallout begin blowing towards me, AND also have the guarantee that the roads wouldn't be gridlocked. That last condition is almost impossible to meet, people will surely get in their cars and drive... somewhere. Which will end up being nowhere, of course, and the ones caught in the fallout will be in trouble. I plan on dragging the mattress over the bathtub in our central bathroom, maybe coat the thing in some aluminum foil, if I have time (not that this would really do much at all for a thick-ish mattress), switching my Geiger counter to the "accrued dosage" mode, and waiting until the rate of increase drops below some threshold that I'll determine as I go along. Maybe 10x the normal/current background rate? But if that's gonna take days, I dunno. I'll have my wife squirrel away a bunch of food and water before we seal up, targeting maybe about 20 - 25 minutes after detonation. That should be before the fallout.. falls... out.

But I did tell my pilot friend to not give a shit what altitude ATC recommends after literally any nuclear strike (in the world) and just get under 1,000 ft. en route to landing somewhere, because nukes instantly populate the radiation belts, and can fling shit into the lower latitudes that we live in. Get as much atmospheric shielding between himself and the energetic particles as possible.

Fun fact that you probably knew: Intelligence organizations monitor the radiation belts relentlessly, because the signature of a significant nuke going off is relatively easy to detect and appears almost instantaneously. You can't hide it. Well, maybe underground testing can obscure it enough to evade detection. Wonder what the threshold of sensitivity is, can't be more than maybe around a few Kt detonated at ground level, I would bet. These are questions I can't/shouldn't ask some of my friends in that field. :/