A lightning strike in a crowded stadium is hazardous out to roughly
50 feet from the strike point, with one or two fatalities and dozens of
injuries. People are occasionally injured 100 feet away from a strike.
This is roughly equivalent to the kill radius and injury radius of a
hand grenade. The mechanisms that hurt us are the millions of volts
of electricity, the heat, and the thunderous blast from the rapidly
expanding air.
Ground current occurs with each strike. You can minimize your
exposure to ground current by keeping your feet close together,
especially avoiding lying flat on the ground. Ground current contributes
to half of lightning fatalities (Fig. 1). This is the primary
mechanism where we can easily reduce lightning risks.
Side flash jumps from tall objects like trees when they are struck by
lightning, so don’t seek shelter near tall trees, other tall objects, or
tall vertical surfaces.
Contact is from touching long conductors like railings, cables,
and fences. Conduct a web search for dead cow lightning to see
morbid images of contact and sideflash.
Upward leaders emanate from high ground and tall objects when
downward leaders approach the ground: even if they don’t connect
with a downward leader, they can be fatal.
Direct strikes cause about 3-5 percent of lightning fatalities. Avoid
high places and open ground to decrease risk of a direct strike.
The explosive force of lightning can cause blunt trauma resulting
in fractures or soft tissue injuries.
We should primarily focus our efforts on avoiding ground
current and side flash.