The negative charge in a storm cloud is attracted to the positive charge on the ground. This attraction causes energy to build up between a storm cloud and the ground. When a large amount of energy builds up, a spark leaves the cloud and heads toward the ground. The negatively charged molecules in the cloud streak behind the spark. This discharge of energy is the lightning seen in the sky.
Lightning strikes the earth almost all the time.
In 1989, the Lightning Detection Network began recording lightning strikes over the 48 continental United States. About half of all flashes have more than one ground strike point. Therefore, at least 30 million points on the ground in the continental United States are struck each year. This tremendous heat provides the third element of the fire triangle discussed in the Fire Science puzzle piece. That is why a fire frequently ignites when lightning strikes fuel.