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Frequently Asked Questions


How strong is lightning and how fast does it move?


Lightning is a giant spark of electricity. A typical lightning flash contains about 20,000 amps and several hundred million volts. This compares to a standard household current of 15 amps and about 115 volts. Typically, a lightning flash is only 1 to 2 inches wide. The step leader that initiates the lightning flash propagates downward from the cloud at a rate of about 320,000 ft per second or about 220,000 miles per hour. The return stroke (the current that cause the visible flash) moves upward at a speed of about 320,000,000 ft per second or about 220,000,000 miles per hour (about 1/3 the speed of light). In comparison, the sound of thunder travels at about 1100 ft per second or about 750 miles per hour. (Answer courtesy of the National Weather Service).