How do lightning bolts form in thunderstorms?
Quick Answer
Lightning forms when charges separate inside a thundercloud, creating a huge electric field that suddenly discharges through air. A typical bolt can carry tens of thousands of amps and heat the air to about 30,000°C.
The Full Story
Inside a thunderstorm, collisions between ice particles, hail, and supercooled water separate electric charges within the cloud. Usually, negative charge builds near the lower part of the cloud while positive charge gathers higher up and on the ground below. When the electric field becomes strong enough, the air breaks down and a stepped leader connects with an upward stream, producing the visible flash. The rapid heating of air causes it to expand explosively, which is why lightning is followed by thunder. A single bolt can travel many kilometres and may be visible from over 100 km away under the right conditions.
Key Facts
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Suggested video title for this topic:
"Why does the sky spark like a giant electric circuit?"