No warning whatsoever. EMP travels at the speed of light, only slowing down when it hits resistance which would be something to take out. The real question is how well does the EM energy couple to the various devices that are vulnerable to being taken out.

Not all cars/trucks are the same and just because it's new tech doesn't necessarily mean it's an easy kill. The EM needs a way into the system and for a car on the road not hooked up to the grid the actual amount of EM energy is not that much per square meter. The national electric grid has these very long antennas which we refer to as power lines. That's why most of the destruction would be done to the grid itself and electronics attached to the grid.

A lot of folks have solar systems on their roof and while they may be susceptible individually, most are also hooked up to the grid. After an event those solar systems are toast.

An AM/FM/SW radio with an antenna deployed is inviting the EM energy in so it might be good to have a back-up or three; AM/FM battery powered radios are cheap. I keep my back-up radios in a steel ammo can. That said, what will you listen to?? I'll bet most radio/TV/cable stations are hooked up to the grid; when they go down, the national ham radio network will be pretty much all that remains in the short term. On that note, I need a VHF scanner for finding local ham transmissions.