Problem: Lightning is the sudden electrostatic discharge that occurs between electrically charged regions of a cloud, between two clouds, or between a cloud and the ground. Thunder that follows a lightening flash comes from the soundwave produced as lightening heat causes the surrounding air to rapidly expand and vibrate. There are an estimated 1.4 billion lightning strikes a year. Reset the map. Add Lightning Frequency. The highest number of lightning flashes per square kilometer occurs in which of the following regions? Need Assignment Help? View Available Hint(s)for Part D Central America Central Africa Western Europe Southeastern United States Southern Australia