Lightning is the result of a build-up of opposing charges within a cumulonimbus cloud. The upper parts of the cloud are usually positively charged and the bottom negative. As this build-up occurs, a positive charge is formed near the ground. These opposing charges are strongly attached to each other. The air in between acts as an insulator. Soon the air between the charges cannot keep them apart any longer and a discharge occurs. The negative charges would ,move to the positive charges in an invisible, jagged, zigzag pattern, called a stepped ladder. A massive electrical current is created. This current is called a thunder bolt. This charge moves very fast at about 96 000 km per second. As the temperature of a thunder bolt can reach 22 000 °C, the air around it is superheated which causes the air around it to expand then contract rapidly. As light travels much faster than sound lightning would be seen first before thunder is heard. To calculate the distance of the storm to where the thunder is heard, count the time in between the lightning flash and the thunder. Every 3 seconds represents one kilometre. There are basically three types of lightning This happens when there is a build up of negative charges at the bottom of a cloud and the ground below is positively charged.   Cloud to cloud lightning occurs when one part of a cloud is charged positive and the other part negative. A discharge occurs in between these two parts of the cloud and cloud to cloud lightning occurs. This also occurs when a positively charge cloud passes a negatively charged cloud, cloud to cloud lightning occurs.   Cloud to air lightning usually occurs when the top of a cumulonimbus cloud which is positively charged. The air surrounding it would be negatively charged. As the differences in charges between the cloud and the air is not as much as in between a cloud and the ground or another cloud, cloud to air lightning is quite weak. Cloud to ground lightning