When lightning strikes
"Lightning is an atmospheric electrostatic discharge accompanied by thunder, which typically occurs during thunderstorms. From this discharge of atmospheric electricity, a leader of a bolt of lightning can travel at speeds of 220,000 km/h (140,000 mph), and can reach temperatures approaching 30,000 °C (54,000 °F), hot enough to fuse silica sand into glass channels known as fulgurites which are normally hollow and can extend some distance into the ground. There are some 16 million lightning storms in the world every year." — Wikipedia
That being said, we have a huge pool of amazing thunderstorm and lightning photography right here on Flickr that is worth more than just one look. If you want to try it yourself, take a look at some of the How to photograph Lightning group discussion threads.