A giant spark
What Is Lightning?
Lightning is the same spark you get from a doorknob, scaled up billions of times.
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Step 1 of 5
Storm clouds are violently churning inside.
Up, down, and colliding, over and over Air rushes up and down at enormous speed, carrying ice crystals and slushy hail with it. Everything is constantly colliding.
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Step 2 of 5
Collisions split the charge apart.
Light ice crystals pick up positive charge and rise. Heavier hail takes negative charge and sinks. The cloud ends up sorted top and bottom.
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Step 3 of 5
The charge difference gets enormous.
Negative at the cloud base pushes negative charge out of the ground below, leaving it positive. The pull between them builds to millions of volts.
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Step 4 of 5
Air normally blocks electricity — until it cannot.
Air is an insulator, which is why the charge builds instead of leaking away. Past a few million volts, the air itself tears open into a conducting path.
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Step 5 of 5
Then everything discharges in a flash.
A faint leader feels its way down, meets a streamer rising from the ground, and the main stroke blasts back up. It takes under a thousandth of a second.
Lightning heats the air to about 30,000°C — five times hotter than the surface of the Sun.
The short version
Lightning is a spark that jumps once a storm cloud has built up millions of volts against the ground.
Try it yourself
Shuffle across a carpet and reach for a metal door handle. That tiny snap is lightning at a scale you can survive.