Being in a pool during a thunderstorm is unequivocally dangerous. Lightning is a massive electrical discharge that seeks the path of least resistance to the ground. Water is a highly effective electrical conductor. A swimming pool is connected to an extensive network of metal plumbing, electrical wiring, and surrounding concrete, all of which can transmit a lethal electrical current from a strike, even an indirect one. This hazard is not limited to a direct hit, making the water and the surrounding pool area an immediate danger during any electrical storm.
How Lightning Strikes Affect Water
The common misconception is that pure water is a poor conductor, but pool water is not pure. The presence of dissolved mineral salts, chlorine, and other chemical impurities dramatically increases the water’s electrical conductivity. This turns the entire pool into a massive conductor during a storm. A single lightning strike delivers an immense charge, which spreads rapidly across the water’s surface.
When lightning strikes the water, the electrical current does not penetrate deeply but radiates horizontally. This creates a lethal electrical field that can extend 20 to 100 meters from the strike point. Even an indirect strike to the ground or a nearby structure can send a current through the pool’s grounded systems. Metal components, such as ladders, handrails, filters, and underground plumbing, act as conductive pathways, introducing the current directly into the water.
Risk Differences Between Pool Types
Outdoor swimming pools carry the highest risk because they are fully exposed to the atmosphere. They are often the highest point in a flat landscape, especially when occupied. The entire surface area and the surrounding wet concrete deck can become energized by a direct or nearby strike. The pool’s connection to underground metal piping and grounding systems provides a ready pathway for the current to travel directly into the water.
Indoor pools, while structurally protected, are still not safe havens during a thunderstorm. The danger is channeled through the building’s infrastructure, including metallic plumbing, electrical conduits, and the grounding system. A lightning strike to the building or nearby ground can send a current through these conductive elements. These elements are physically connected to the pool water through systems like recirculation pumps and drainage. Hot tubs and spas present a similarly high risk due to the close proximity of users to highly conductive electrical components, such as control panels, pumps, and heating elements.
Essential Safety and Evacuation Protocols
Immediate evacuation from the water is required the instant thunder is heard or lightning is seen, as lightning can strike from storms many miles away. Safety experts utilize the “30/30 Rule” to guide evacuation and return times.
The first “30” refers to the flash-to-bang count: if the time between seeing the lightning flash and hearing the thunder is 30 seconds or less, the storm is close enough for a strike, and all water activities must cease. Once the pool is evacuated, everyone should seek shelter in a substantial, enclosed building that is fully wired and plumbed, or inside a hard-topped, all-metal vehicle.
Unsafe shelters include open structures like gazebos, sheds, covered patios, and areas under tall, isolated trees, as these offer no protection from a strike. The second “30” requires waiting a minimum of 30 minutes after the last sound of thunder or flash of lightning before it is safe to return to the pool or surrounding area. If caught in the open with no immediate shelter, individuals should crouch down low with their head tucked and hands over their ears, minimizing contact with the ground.