It may be safe to say in a car while lightening or thunder strikes is throwing tantrums probably because the car insulator is working perfectly fine but it's not safe nor advisable to drive when it's raining with lightening or thunder strikes taking place. The reason for this is that when it's raining, the road becomes too wet and slippery which causes accidents to happen easily because the car tyres would lose its footing too easily and brakes wouldn't work well 100 percent. Also, the vision of the car driver is hampered by the rain thereby making it impossible to have a good look on the road he or she is driving on and this is very risky. Coming to the part of thunder and lighting, even though it may not strike the car, it can strike other things that might fall onto the road and cause accidents. So, it's not entirely safe.