What is a lighting strike? Are the gods angry? I hope not.
Lightning is an electrical discharge produced to balance the differences between positive and negative charges within a cloud, between two clouds, or between the cloud and the ground.
Inside a cloud, water and ice are moved about. They are moved up by warm air, down by gravity, and also compressed within the cloud.
Just as rubbing a balloon can create static electricity, the particles in the cloud become charged. Positive charges move up and negative charges move down. The negative charges in a cloud seek positive charges on the ground, and if the difference between these charges becomes sufficiently strong, the normal insulating qualities of the air break down.
First, a usually invisible discharge of electrons race down from the cloud. Then a second bolt races upward to meet the descending charge, and it is when they connect that you see a lightning bolt.