Lightning Is More Dangerous Than Most People Think
Lightning kills an average of 20 people and injures hundreds more in the United States each year. The majority of victims are struck while outdoors during warm-season afternoon thunderstorms, and two-thirds of lightning deaths occur in people who had time to reach safety but did not. Understanding a few straightforward safety rules can dramatically reduce your risk.
1. Use the 30-30 Rule
The 30-30 rule is the simplest and most effective guideline for lightning safety. When you see a lightning flash, count the seconds until you hear thunder. If the interval is 30 seconds or less, the storm is within 10 kilometers (about 6 miles) and you should immediately seek shelter. After the last flash or thunder, wait at least 30 minutes before returning outdoors.
Lightning can strike from the edge of a storm cell. Bolts from the blue have been documented striking ground more than 40 kilometers from the storm center, which is why the 30-minute wait after the last thunder is critical. Many lightning fatalities occur when people return outdoors too soon.
2. Seek a Substantial Building or Hard-Topped Vehicle
The safest place during a thunderstorm is inside a fully enclosed building with wiring and plumbing. If a building is not available, a hard-topped vehicle with the windows closed provides good protection. The metal frame of the vehicle conducts the current around the occupants and into the ground, a principle known as a Faraday cage effect.
Open structures such as picnic shelters, bus stops, porches, and gazebos do not provide protection from lightning. Neither do tents, sheds, or small open-air structures.
3. Avoid Isolated Tall Objects
Lightning tends to strike the tallest object in an area, although this is a tendency rather than an absolute rule. When caught outdoors, stay away from isolated trees, utility poles, flagpoles, and metal fences. If you are in an open field, you yourself may be the tallest object, so move to lower ground if possible without entering a flood-prone area.
If you are hiking and a storm approaches, descend from ridges, peaks, and exposed terrain. Avoid cliff edges and cave entrances, which can channel ground current. Dense forest at lower elevation is preferable to an isolated tree or open summit.
4. Get Out of and Away from Water
Water is an excellent conductor of electricity. If you are swimming, boating, or near a body of water when thunder begins, exit the water immediately and move well away from the shoreline. Lightning striking water can send lethal current hundreds of meters across the surface. Fishing, kayaking, and sailing are among the higher-risk outdoor activities during thunderstorms.
5. Avoid Plumbing and Corded Electronics Indoors
When sheltering indoors during a storm, avoid contact with plumbing fixtures. Do not shower, bathe, wash dishes, or wash your hands during active lightning. Metal plumbing pipes can conduct current from a lightning strike on the building or nearby ground into the water supply. Similarly, avoid using corded telephones and plugged-in electronics. Cordless phones, laptops on battery power, and cell phones are safe to use.
6. Stay Away from Windows and Doors
Side flashes can jump from metal window frames, door frames, or concrete walls to a person standing nearby. During intense storms, move to an interior room away from windows. Concrete floors and walls may contain metal reinforcing bars that can conduct current, so avoid leaning against them.
7. If Outdoors with No Shelter, Minimize Contact with the Ground
If you are caught outdoors with absolutely no shelter available, crouch down with your feet together, minimizing your contact with the ground. Do not lie flat, as this increases your surface area exposed to ground current. Put your hands over your ears to protect against the acoustic shock of nearby thunder. This position is a last resort, not a substitute for seeking real shelter.
8. Separate from Your Group
If you are with a group of people outdoors during a thunderstorm, spread out. Maintain a distance of at least 6 meters (20 feet) between individuals. This reduces the chance that a single strike or ground current event will injure multiple people, and ensures that uninjured members of the group can provide first aid.
9. Monitor Weather Forecasts and Lightning Tracking Apps
The best safety strategy is avoidance. Check weather forecasts before outdoor activities, especially during thunderstorm season. Real-time lightning tracking tools can alert you to approaching storms before you hear thunder. States like Florida, Texas, and Oklahoma experience especially frequent thunderstorms during their peak seasons.
10. Know How to Help a Lightning Strike Victim
A person struck by lightning does not carry an electrical charge and is safe to touch immediately. Call emergency services (911) right away. Lightning strike victims are most likely to die from cardiac arrest. If the person is unresponsive and not breathing, begin CPR immediately. Many lightning strike victims can be revived with prompt medical attention.
Common injuries from lightning strikes include cardiac arrest, burns (often superficial), neurological damage, hearing loss from the thunder blast, and eye injuries. Even if a victim appears alert, they should be evaluated at a hospital, as some effects (particularly neurological and cardiac) may be delayed.
Common Lightning Myths Debunked
Myth: Rubber tires protect you from lightning
The rubber tires on a vehicle do not provide insulation against lightning. A lightning bolt that has traveled through kilometers of air (which is an excellent insulator) will not be stopped by a few centimeters of rubber. What protects vehicle occupants is the metal frame conducting the current around the passenger compartment, not the tires. This is why convertibles and fiberglass-bodied vehicles do not offer the same protection.
Myth: Lightning never strikes the same place twice
This is entirely false. Lightning frequently strikes the same location repeatedly, especially tall, pointed, or isolated structures. The Empire State Building is struck roughly 20 to 25 times per year. Communication towers, wind turbines, and tall trees are struck repeatedly throughout their lifetimes. If a location has been struck once, it is likely because its physical characteristics make it a favorable strike point, and those characteristics do not change.
Myth: If it is not raining, there is no lightning danger
Lightning can strike well ahead of or behind the rain shaft of a thunderstorm. So-called "bolts from the blue" can travel horizontally for tens of kilometers before turning toward the ground. Dry thunderstorms, which produce lightning but little or no rain at the surface, are common in the western United States and are a major cause of wildfire ignitions.
Myth: Metal attracts lightning
Lightning is not attracted to metal. The path of a lightning channel is determined by the conductivity and geometry of the air and objects below the cloud, not by the composition of those objects. However, metal is an excellent conductor, so if lightning does strike a metal object, the current will flow through it efficiently, which is why metal objects can be dangerous to touch during a storm but also why metal-framed buildings provide effective shelter.