Video narration
How does lightning form in a storm cloud, and why does thunder follow the flash? Inside a storm cloud, rising and falling winds keep ice and water droplets colliding. These collisions separate electrical charges, so opposite charges build up in cloud regions. As the difference grows, the electric field between cloud and ground-or within clouds-becomes strong. But lightning is not fire made inside a cloud. It is an electrical discharge: the field breaks down the air and creates a conducting path. Energy rushes through it, producing the flash. That lightning heats air so rapidly, it expands and creates thunder. You see the flash first because light travels much faster than sound. So the answer is: collisions separate charge, a powerful field breaks the air, and the discharge becomes lightning. During storms, avoid open fields, tall trees, and metal.