Weather Tidbits: How Lightning Is Formed

This edition of Weather Tidbits will discuss how lightning forms. Lightning sparks when molecules of opposite charges come into contact. During the formation of a thunderstorm cloud, the top of the cloud becomes positively charged and the base of the cloud becomes negatively charged. The charge distribution within the cloud is caused by collisions between various hydrometers such as raindrops, ice crystals, and hail. This distribution forces molecules of negative charge at the surface to repel away from the cloud and molecules of positive charge to accumulate together below the negatively charged cloud base. This is because molecules of opposite charge attract each other. Molecules of the same charge repel each other. As the thunderstorm matures, updrafts of rising air form. The thunderstorm’s updraft carries the positively charged molecules upward from the ground, bringing them closer to the negatively charged molecules. When the negatively and positively charged molecules make contact, a rapid discharge of electricity occurs in the form of a lightning strike.

Lightning is not just limited to cloud to ground strikes. Other types of lightning include cloud to cloud, cloud to sky, ground to cloud, and intracloud (within the clouds). Intracloud and cloud to ground are the most common. Cloud to cloud and ground to cloud are less common. All types of lightning involve the interaction of opposite charges.