A return stroke carries ~30,000 A (a thousand times a hair-dryer) and heats the channel to ~30,000 °C — five times the Sun's surface. The channel's explosive expansion is thunder; light reaches you instantly but sound crawls at ~1 km every 3 s, so count seconds ÷ 3 = km (÷ 5 for miles). Most flashes never reach the ground at all — intra-cloud lightning is the most common kind.

30/30 rule: if thunder follows lightning within 30 s, go indoors; wait 30 min after the last thunder. Contrary to myth, lightning can strike the same place twice (the Empire State Building is hit ~20× a year), and rubber-soled shoes protect you about as much as wishes.