What causes lightning?

Clouds hold fragments of ice, both big and small. Each time the ice fragments crash into each other, some electricity is made. Little by little, this electricity is stored up in the cloud. When the cloud can’t hold all the electricity any more, the electricity suddenly flows in one big jolt toward the ground. This is how lightning works.

But have you wondered why we see flashes of light and hear loud rumbling sounds? In the instant that the electricity flows toward the ground, it heats up air molecules to very high temperatures over 10,000 degrees Celsius. This makes the air molecules move violently. The movement of air molecules causes the flashes of light and loud thunderclaps. Air normally does not let electricity pass through it. For lightning to happen, an enormous electric force of around 100 million volts builds up in the cloud. With this much force behind it, electricity pushes its way through the air and heads toward the ground. This is why we see lighting follow a zigzag path, rather than moving in a straight line.