I’ve always been told that cars are decent places to ride out a thunderstorm, because the steel structure means that the cabin is protected in the same way as a Faraday cage (I think that’s what those birdcage looking things are called, anyway). Can the same be said of a convertible car? Does a convertible offer the same or less protection against lightining strikes as does a hardtop?
My first instinct says no. As lightning goes from the ground up, there would be nothing in my opinion that would prevent a “streamer” going from your head, and becoming a bolt. I could be wrong but I’m reasonably sure you could get struck.
Isn’t the “cars are safe in thunderstorms” idea based on the rubber wheels more than the Faraday cage? You’re safer because you’re not grounded?
I think that a bigger problem would be all that wind whipping around messing your hair up. Combine that with some blowing rain and Oh Nellie!, we have got us one fashion disaster.
No. Consider this: lightning can pass through ten to twenty miles of air (a reasonably good insulator under normal conditions) before striking ground. A few inches of rubber at the end of the path is NOT going to stop it. The metal body of the vehicle is what affords you the protection by conducting the electricity around you and out the bottom, to Earth.
A convertible with a fabric top will not offer the same level of protection as a car with an all-metal body. Neither will a car whose body is composed primarily of an insulator, such as fiberglass.
I recall seeing somewhere that your tires would have to be much, much, much thicker to provide any protection at all. Like, many hundreds of times thicker than actual tires are.
No, the rubber wheels don’t do much. They have steel belts and are probably going to be wet anyway. It’s mostly the metal cage giving the electricity a better route to ground than through you.
While I would * guess * convertibles would be less safe, they probably aren’t substantially so. They are required to have built-in roll bars (probably steel and conductive), and they’re generally pretty low to the ground, so unless you’re on a flat treeless area like a golf course (or Kansas), the car is not likely to be the most attractive target. Just tailgate the nearest SUV and you’ll probably be OK 
They tested this with a non-convertible on the “Top Gear” show in the UK. They put it right under a generator, and the bolt jumped right to the car no problem and down the hood to ground. Definitely Faraday cage and not the rubber.
With regard to the term “faraday cage” with respect to a metal car body, this is a somewhat misleading explanation for why you don’t get shocked. Faraday cages actually address electrostatic charge and demonstrate that the net charge within a volume suitable enclosed by a conductor will be zero, analogous to the zero net gravity within a massive shell.
It is true that the metal shell of the vehicle conducts the electric current to ground (or nearly so) via the skin effect but a car body is a very imperfect faraday cage; you can test this yourself by using a cell phone within a car. Because of the large, electromagnetically-transparent openings, electromagnetic waves are readily conducted right through the body, whereas in a properly ray-shielded container you would get little or no transmission.
What saves you from being struck by lightning while inside your car is that a) the glass is a very poor conductor of electricity and b) the metal body is an excellent conductor and sits lower to ground, therefore making a less resistive path than anything else. Also, the most “pointy” parts of a car are usually metal–the radio antenna, fitings, et cetera–and are most likely to be the strike point for a lightning bolt. A convertible fails to provide the same protection as it doesn’t have a conductive path overhead, though I would expect that the metal body would be more attractive.
To state this another way; if you’re in a car that is entangled in a downed (live) power line, opening the car door isn’t going to kill you by creating an unbalanced charge. But stepping out and putting your foot on the ground, making a direct path from the powerline → car body → your body → ground will cause you to be electrocuted.
In any case, the thin rubber tires on your car are not going to protect you against a charge so powerful that it has conducted itself several miles by ionizing a path through air. What protects you is that the steel or aluminum of the car body has much higher conductance than you. Think about that next time someone complains about how resistive you are to change. 
Stranger