Lightning is a very powerful electrical discharge made during a thunderstorm. The electric current makes the air very hot. The suddenly heated air expands very quickly, which causes thunder. Sometimes lightning happens between clouds. Sometimes (in the rain) lighting goes from cloud to ground. If it goes from cloud to ground, it can strike a person. Around 2000 people are struck by lightning each year. About 50 to 100 lightning bolts strike the Earth every second. Lightning has hit the Empire State Building as many as 500 times a year.