Annual Probability of Being Within 500 Feet of a Lightning Strike

The United States experiences approximately 25 million cloud-to-ground lightning strikes per year, and it is estimated that about 5% of Americans (15-16 million people) are within 500 feet of a lightning strike at some point during the year. Florida has the highest lightning density, followed by the Gulf Coast and central states.

While being within 500 feet of a strike is a notable experience (the thunder is deafening, the flash blinding, and the ground may shake), the actual injury zone is much smaller. Lightning can kill or injure people through direct strike, side splash (jumping from a nearby object), ground current (electricity spreading through the ground), and contact with a struck object. About 20 people are killed and 100-200 injured by lightning in the US each year, down from about 400 deaths per year in the early 1900s.

The decline in lightning deaths is attributed to improved warning systems, fewer people working outdoors, more substantial buildings, and better public awareness. The "30-30 rule" is the primary safety guideline: go indoors when the time between lightning flash and thunder is 30 seconds or less, and stay inside for 30 minutes after the last flash. No outdoor location is safe during a thunderstorm, and small shelters (picnic shelters, bus stops) do not provide adequate protection.