What is lightning? Lightning is a form of electrical discharge between clouds or between a cloud and the ground. The discharge may take place between two parts of the same cloud, between two clouds, or between a cloud and the ground. Lightning may appear as a jagged streak, a flash in the sky, or in the more rare form of a brilliant ball. Thunder is the sound waves produced by the explosive heating of the air in the lightning channel during the return. Lightning Facts: Most lightning strikes occur either at the beginning or end of a storm. The average lightning strike is six miles long. Lightning reaches 50,000 degrees Fahrenheit, fours times as hot as the sun's surface. A cloud-to-ground lightning channel can be 2 to 10 miles long. Voltage in a cloud-to-ground strike is 100 million to 1 billion volts. In Florida, lighting bolts kill an average of 10 people per year. Authorities say that 90% of Florida's recent wildfires were started by lighting. Thunderstorms produce more than a million lightning strikes per year.