Lightning begins inside storm clouds, where colliding ice particles, water droplets, and graupel generate separated electrical charges. Typically, the upper portion of a cloud becomes positively charged while the lower portion becomes negatively charged. When the charge separation grows large enough, the insulating capacity of the air breaks down.
A stepped leader—an invisible channel of negative charge—zigzags downward from the cloud in rapid increments. As it nears the ground, upward streamers of positive charge rise from tall objects, structures, and even people. When a leader and a streamer connect, a conductive path opens, and the return stroke surges upward. That return stroke is the brilliant flash we see.
The current in a return stroke can reach tens of thousands of amperes. The channel heats the surrounding air almost instantaneously to temperatures on the order of tens of thousands of degrees—several times hotter than the surface of the sun. The explosive expansion of that superheated air produces the shockwave we hear as thunder. Since sound travels roughly one mile every five seconds (or one kilometer every three seconds), counting the seconds between the flash and the thunder tells you how far away the storm is.
The Different Ways People Are Struck
Many people assume a lightning strike means a bolt hitting the body directly. In reality, direct strikes account for only a portion of lightning injuries. The main mechanisms include:
- Direct strike. The bolt attaches to a person directly, usually someone in an open area. This is the least common but often the most severe mode.
- Side flash (side splash). Lightning strikes a taller object nearby—such as a tree—and part of the current jumps to a person standing close to it. Sheltering under a tree in a storm is one of the most dangerous choices a person can make.
- Ground current. When lightning strikes the ground or a structure, current spreads outward through the soil. Anyone standing nearby can receive a portion of that current through their legs. Ground current injures large numbers of people, including herds of livestock in open fields.
- Conduction (contact voltage). Lightning travels through plumbing, wiring, fences, or metal surfaces. A person touching a faucet, a wired phone, or a metal fence during a storm can be injured even indoors.
- Streamers. Upward-moving charges that do not complete a full strike can still injure people on ridgelines, peaks, or tall objects.
This variety matters for safety: staying away from tall isolated objects, spreading out in groups, and avoiding conductive paths are all based on how these mechanisms actually work.
What a Strike Does to the Human Body
Lightning injuries are different from typical electrical injuries. A strike lasts only milliseconds, and much of the current can flash over the outside of the body rather than passing through it. Contrary to widespread belief, the majority of people struck by lightning survive. However, survivors often face serious, sometimes lifelong consequences.
The most common cause of death from a lightning strike is cardiac arrest: the massive electrical surge disrupts the heart's rhythm and can stop breathing when the respiratory control centers of the brain are affected. Injuries among survivors can include:
- Neurological problems, such as memory difficulty, concentration problems, mood changes, sleep disturbance, and chronic pain
- Burns, usually superficial, sometimes with a fern-like pattern on the skin known as Lichtenberg figures
- Hearing damage from the thunder's shockwave at close range, including eardrum rupture
- Eye injuries, including cataracts developing after the event
- Fractures and muscle injuries caused by the violent muscular contraction of being thrown
Helping Someone Struck by Lightning
Two facts guide first aid. First, lightning victims carry no electrical charge—you can touch and treat them immediately. Second, unlike many emergencies, a victim may appear dead because breathing and heartbeat have stopped, yet prompt response can save them.
If someone is struck:
- Make sure the scene is safe. If the thunderstorm is still overhead, move yourself and the victim to shelter when possible. Lightning can strike the same place more than once.
- Call emergency services immediately.
- Begin CPR if the person is not breathing or has no pulse. Cardiac arrest from lightning is a primary killer, and bystander CPR is often decisive.
- Treat for shock by keeping the person warm and lying down, and monitor them until help arrives.
People struck by lightning pose no danger to responders, and there is no reason to delay care.
What Lightning Does to Buildings and Property
A strike to a structure can ignite fires, shatter concrete and masonry, and destroy electrical systems. The damage usually comes through several routes:
- Fire, when the bolt or conducted current ignites roofing, framing, or stored materials
- Structural damage, from the explosive heating of moisture inside concrete, brick, or trees
- Power surge damage, as the enormous surge travels through wiring and destroys electronics, appliances, and connected equipment
- Plumbing hazards, since water and metal pipes conduct electricity
Surge protectors help shield individual electronics from smaller surges, but they are not designed to handle a direct strike. Comprehensive protection requires a properly installed lightning protection system.
The 30-30 Rule and Other Safety Basics
Meteorological agencies such as national weather services recommend the 30-30 rule as a simple guideline:
- If the time between seeing lightning and hearing thunder is 30 seconds or less, the storm is close enough to strike you. Go inside immediately.
- Wait at least 30 minutes after the last thunder before returning outdoors. Many strikes occur as a storm appears to be leaving.
Safe shelter means a substantial building with plumbing and wiring, or a hard-topped metal vehicle with the windows closed. The vehicle's metal shell conducts current around the occupants—it is not the rubber tires that protect you. Convertibles, golf carts, open shelters, picnic pavilions, and dugouts offer little or no protection.
While sheltering indoors:
- Stay off corded phones and plugged-in electronics
- Avoid contact with plumbing—no showers, baths, or dishwashing
- Keep away from windows, doors, and porches
- Unplug sensitive equipment before the storm arrives if you can do so safely
If you are caught outside with no shelter available, avoid hilltops, open fields, tall isolated trees, water, and metal objects. Keep moving toward a vehicle or building. As a last resort, crouch low on the balls of your feet with your feet together, minimizing contact with the ground—but do not lie flat, since lying down increases exposure to ground current.
Common Myths That Get People Hurt
- "Lightning never strikes the same place twice." False. Tall structures such as skyscrapers and towers are struck repeatedly, sometimes dozens of times a year.
- "Rubber-soled shoes protect you." False. The voltage and current involved are far beyond anything footwear could insulate.
- "Metal attracts lightning." Misleading. Lightning is not attracted to metal; it follows the easiest path to ground. Metal does not draw strikes, but it does conduct current efficiently, which is why touching metal during a storm is dangerous.
- "A tree is good shelter." Dangerous. Trees are among the deadliest places to shelter. Side flash and ground current injure people standing beneath them.
- "If it's not raining, I'm safe." False. Lightning can strike more than ten miles from the rain core of a storm—the origin of the phrase "a bolt from the blue."
A rare warning sign that a strike may be imminent is your hair standing on end or a buzzing sound on nearby metal objects. If this happens, assume the crouch position immediately and seek shelter the moment the danger passes.
Protecting Your Home
If you live in an area with frequent thunderstorms, a lightning protection system is worth considering. A modern system includes air terminals (lightning rods) on the roof, conductors that carry current down the structure, and grounding rods that dissipate the charge safely into the earth. Installed to recognized standards by qualified contractors, these systems do not attract lightning—they simply provide a controlled path for a strike that would otherwise find its own destructive route through your home. Whole-house surge protection adds a second layer of defense for your electrical and electronic equipment.
The Bottom Line
Lightning is fast, powerful, and largely predictable in its behavior even when individual strikes are impossible to forecast. Most injuries and deaths are preventable. Track the storm, respect the 30-30 rule, get inside a real building or a hard-topped vehicle, avoid conductive paths indoors, and never shelter under a tree. If someone is struck, they carry no charge—call for help and start CPR if needed. Those simple habits separate the people who walk away from lightning season unharmed from those who do not.