When lightning strikes, the surface rubs electrons from the lightning, and a spark of electricity shoots from the lightning to the surface. In a thunderstorm, the lower cloud has as many as 100 million volts of electricity. This electricity is given out either within the cloud, to the ground, to another cloud, or into the air. Lightning has been known to travel from the ground upwards to the cloud. In 1993, scientists discovered lightning bolts that shot upward from the top of a cumulonimbus cloud.