Lightning's visible flash travels at the speed of light, approximately 670 million miles per hour (or about 186,000 miles per second). However, the electrical discharge of lightning itself moves slower. The initial part of a lightning strike, called the stepped leader, travels at around 150,000 meters per second (about 335,000 mph), which is roughly one two-thousandth the speed of light. The return stroke, which produces the bright flash we see, travels at about 100 million meters per second, roughly one-third the speed of light, or about 220 million mph. The typical speed of the electrical discharge is around 270,000 mph but can fluctuate depending on atmospheric conditions.