As per my answer under Animals and Nature on the subject of Thunderbolts if you are really keen I would head to the Northern Territories of Australia during the rainy season, I saw the three astonishing thunderstorms there, 1 at Katherine, 1 off the coast of Darwin and 1 in Kakadu National park.... unbelievable. If that's a bit far from home and assuming you're in the UK I'd suggest the West coast of Ireland or Scotland. Maybe the Isle of Skye, the Cullin Mountains provide a stunning backdrop and you get some impressive storms there.