Indoors Is Safer, but Not Risk-Free
The National Weather Service recommends getting inside a substantial building as soon as thunderstorms threaten. This is sound advice: the overwhelming majority of lightning fatalities occur outdoors. However, many people assume that once they step inside, the danger is completely over. It is not. According to NWS data, approximately one-third of lightning injuries occur indoors. Understanding what makes indoor lightning injuries possible, and how to prevent them, is essential for anyone living in lightning-prone regions.
Lightning can enter a building in three primary ways: a direct strike to the roof or structure, through wires and pipes that connect the building to the outside, or through the ground via conductive pathways like plumbing, electrical grounding, and metal frameworks. Once inside the building's infrastructure, the electrical current follows the path of least resistance, which may include wiring, plumbing, phone lines, cable TV connections, and metal structural elements.
Stay Away from Windows and Doors
During an active thunderstorm, position yourself in an interior room away from windows, doors, and exterior walls. Windows are a risk for two reasons. First, a lightning strike near the building can produce a side flash, a secondary discharge that arcs from the strike point to nearby objects, and an open window provides a direct path for this arc to enter your living space. Second, severe thunderstorms often produce strong winds and hail that can shatter glass, causing injuries independent of the lightning itself.
Sliding glass doors, screened porches, and open garage doors are all potential entry points for lightning-related hazards. If your home has a covered porch with metal railings or supports, avoid leaning against these during storms, as metal can conduct a strike's current into the structure.
Avoid Plumbing During Storms
One of the most important and least-followed rules of indoor lightning safety is to avoid all contact with plumbing during thunderstorms. This means: do not shower, do not take a bath, do not wash dishes, and do not wash your hands if you can avoid it.
The reason is straightforward. Most residential plumbing uses metal pipes, at least in some sections of the system, and these pipes run from inside the house to the outside where they connect to the municipal water supply or a well. If lightning strikes your home or nearby, electrical current can travel through these pipes and reach anyone in contact with the water. Even homes with PVC pipes may have metal connections, fittings, or grounding wires that provide a conductive pathway.
The risk is real. The CDC documents cases of people injured by lightning while showering, and plumbing-related lightning injuries are a consistent category in NWS injury reports. The safest approach is simply to wait until the storm passes. A 30-minute delay in your shower is a trivial inconvenience compared to the consequences of a lightning injury.
Unplug Electronics and Use Surge Protection
Lightning-induced electrical surges are one of the most common causes of property damage during thunderstorms. A lightning strike on or near a power line can send a voltage spike of tens of thousands of volts through the electrical system, destroying anything connected to it. Computers, televisions, routers, gaming consoles, and smart home devices are all vulnerable.
The most reliable protection is to unplug electronics before the storm arrives. This eliminates the conductive path entirely. If you wait until the storm is overhead, it may already be too late, as surges travel at nearly the speed of light through wiring.
For electronics that remain plugged in, surge protectors provide a meaningful layer of defense. However, not all surge protectors are equal. Look for these specifications:
- Joule rating: Higher is better. A minimum of 2,000 joules is recommended for computers and home entertainment systems.
- Clamping voltage: Lower is better. This is the voltage level at which the surge protector begins diverting excess energy. Look for 400 volts or less.
- Response time: Measured in nanoseconds. Faster response times provide better protection. One nanosecond or less is ideal.
- UL 1449 certification: Ensure the device is tested and certified by Underwriters Laboratories to the current standard.
Even the best point-of-use surge protectors cannot fully protect against a direct lightning strike to your home or a nearby transformer. For comprehensive protection, consider a whole-house surge protector, which is installed at your electrical panel and protects every circuit in the home simultaneously.
Whole-House Surge Protection
A whole-house surge protection device (SPD) is installed at the main electrical panel by a licensed electrician. It works by diverting excess voltage from the incoming power lines to the grounding system before it reaches any of your home's circuits. These devices typically cost between $200 and $500 for the unit, plus professional installation.
Whole-house SPDs are rated by their maximum surge current capacity, measured in kiloamps (kA). For homes in lightning-prone areas, a minimum rating of 50 kA is recommended. Many electrical codes in lightning-heavy states now encourage or require whole-house surge protection in new construction.
For the best protection, use a layered approach: a whole-house SPD at the panel plus point-of-use surge protectors at individual outlets for sensitive electronics. This two-stage system catches surges at the entry point and again at the device level.
Corded Phones and Ethernet Cables
Corded landline telephones are directly connected to outside phone lines that can carry lightning surges. Using a corded phone during a thunderstorm is one of the oldest known causes of indoor lightning injury. While landlines are less common today, they still exist in many homes and businesses.
Similarly, hardwired Ethernet connections that run from an external cable or DSL entry point can carry surges into your home network equipment and computer. If your internet connection enters the building through a cable that runs outdoors, consider using an Ethernet surge protector or disconnecting during severe storms.
Cordless phones, cell phones, and Wi-Fi-connected devices are all safe to use during thunderstorms, as they have no direct wired connection to the outside.
Lightning Rods and Home Protection Systems
Lightning rods, more properly called air terminals, have been protecting buildings since Benjamin Franklin demonstrated their effectiveness in the 18th century. A modern lightning protection system consists of several components working together:
- Air terminals (rods): Pointed metal rods installed at the highest points of the roof and at regular intervals along ridgelines.
- Conductor cables: Heavy copper or aluminum cables that connect the air terminals to each other and route current down the outside of the building.
- Ground rods: Metal rods driven deep into the earth, providing a low-resistance path for lightning current to dissipate safely into the ground.
- Bonding connections: Cables that connect the lightning protection system to the home's electrical grounding, plumbing, and any other metal systems, ensuring all conductive paths are equalized.
A properly installed lightning protection system does not prevent lightning strikes. Instead, it provides a preferred, low-resistance path for the current to follow, directing it safely around and away from the building's occupants and contents. The system should be installed by a certified professional and should comply with NFPA 780 (the Standard for the Installation of Lightning Protection Systems) and UL 96A.
Apartments and High-Rise Buildings
Residents of apartment buildings and high-rises may assume they are inherently safe from lightning, but the same indoor precautions apply. Large buildings often have steel frameworks that conduct lightning current, and surges can still travel through electrical and plumbing systems. Follow the same guidelines: avoid plumbing, unplug sensitive electronics, and stay away from windows.
High-rise buildings are actually more likely to be struck by lightning than low-rise structures, simply because they are taller. However, the steel-frame construction of most modern high-rises provides excellent lightning conduction, directing current through the building's structural steel to the ground without harming occupants, provided they follow basic indoor safety rules.
Know When Storms Are Coming
The best indoor lightning safety strategy starts before the storm arrives. Monitor local weather forecasts during thunderstorm season, and use real-time lightning tracking tools to know when storms are approaching your area. Our Florida lightning map and state-level maps provide real-time visibility into active thunderstorms. For more safety guidance, read our comprehensive lightning safety tips guide.