In Griffiths' Introduction to Electrodynamics, at the Electrostatics chapter, in particular, in the conductors section, he says this after the stating that within an empty cavity surrounded by a conductor material, the electric field is 0:
"(...) This is why you are relatively safe inside a metal car during a thunderstorm - you may get cooked, if lightning strikes, but you will not be electrocuted".
So, in a conductor, if I bring (for example) a positive charge q outside the conductor, induced negative charge will appear at its surface, negating the positive charge, killing off the field of q for points inside the conductor. My question is: how fast does such process occurs in order to negate the charge of a lightning strike, "protecting" me inside the cavity (interior of the car)?