The protons in the object begin to form a traveling spark upward towards the stepped leader. When the stepped leader and traveling spark come together, a powerful electrical current starts to flow, creating the lightning stroke . On contact, a powerful wave of protons travel up the lightning stroke at about 60,000 miles per second, illuminating the path, creating the return stroke . This is the light we see. There can be several waves of protons traveling up the path, creating more and more return strokes, and more and more flashes, making the lighting flicker.
Thunder is created when the lightning's energy is converted into heat and then sound waves.
This causes the air to expand. The expanding air then cools, and contracts. This quick expansion and contraction of air causes the air molecules to move back and forth, creating sound waves. If this is not possible, take cover immediately in a sturdy building. An automobile can also offer fair protection.