Lighting is produced by thunderstorms and are represented by a flash of electricity. When there is a thunderstorm there are lightning strikes. Each flash of lighting is considered to be very dangerous and have killed between 75 to 100 people each year, more than hurricanes and tornadoes, according to Weather Wiz Kids.
When a positive and negative charge in a cloud separate, lightning is produced.
The charge separation is not understood completely but several things are needed to complete the process. The first two are ice pellets and rising air, both which are found in cumulonimbus clouds, generally in the late-spring and summer. Ice pellets collide and through this collision pick up net charges. They are then sorted by updrafts. This leaves large negatively charged pellets at the bottom as it takes greater energy to move larger particles. Smaller, positively charges pellets move to the top of the clouds. The negative charge continues to grow, then it draws a positive charge on the surface of the earth. This occurs because opposite charges are drawn to each other. The negative charge continues to grow until it leaves the cloud for the surface. This is the first stage of lightning.
According to NOVA, lightning can travel through the air for quite a distance, “beyond the range of thunder” to areas with blue sky. These are called “bolts from the blue” and can be seen even in locations where there are not any clouds. This first stage is called a stepped leader. It creates a pathway of electricity. When it nears the ground, a positive charge is elicited creating a strong electrical attraction. In an effort to reach the stepped leader, the positive charge rises from the ground or from items, like people or houses, which rise up from the ground. This creates a streamer. When the two meet, the electrical circuit is complete. The negative charges from the leader travel to the ground first, then the charges higher up the leader. This return stroke is conductive so paves a path to the ground. Frequently, many follow-up stokes occur through this same pathway. Each one drains some of the negative charge from the cloud. This is seen as a flickering from those on the ground.
Lightning usually occurs either within a cloud, or between clouds. However, there have been occasions when the sky is clear, yet lightning still strikes. This is unusual but it does happen. When this happens a lighting strike may travel several miles before it makes contact. This can happen when the sky appears blue when the lightning hits.