Cloud-to-ground lightning is by far the most dangerous form of lightning. Although this type of lightning is not the most common type, it is the easiest to research. Therefore, we know the most about cloud-to-ground lightning. Most cloud-to-ground strikes begin near the lower portion of the cloud. As shown below, the lower portion of the cloud is negatively charged. This results in the lightning delivering negative charge to the ground. There are, however, a small percentage of flashes that carry positive charge to the earth. These flashes do not typically occur during the middle of a thunderstorm when there is a “bank” of negative charge between the top, positively charge portion, of the cloud and the ground. Usually, these types of strikes occur when the thunderstorm is dissipating and there are not as many negatively charged particles built up between the top of the cloud and the ground. These flash are also more prominently found during the winter months than during the summer months. This is possibly caused because the cold winter air does not create as many updrafts to lift the smaller, positively charged particles to the top of the cloud. A third way for lightning to cause a net transfer of positive charges to the earth is when there is a tall Earth grounded object. This will be explained in more detail under “Description of Lightning Discharge Processes”.