Swimming in an outdoor pool during a thunderstorm is not safe. Lightning strikes present a severe danger, as the massive electrical charge travels instantly through the water and the pool’s infrastructure. The risk of electrocution or serious injury is extremely high, even if the lightning does not strike the water directly. A rapid evacuation is necessary when a thunderstorm is near.
The Primary Hazard: Electrical Conductivity
The danger is rooted in the conductivity of the water and the pool’s construction materials. While pure water is a poor conductor, outdoor pools contain dissolved minerals, salts, and chemicals like chlorine that introduce ions and significantly increase the water’s electrical conductivity. If lightning strikes the water, the electrical current spreads rapidly across the surface, creating a wide danger zone.
A single lightning bolt can deliver immense power, often reaching up to 300 million volts and 30,000 amps, which is more than enough to cause fatal electrocution. This puts anyone in the pool at risk, even if they are a considerable distance from the strike point.
The risk extends beyond the water itself, as the pool’s metal components and plumbing systems are highly conductive pathways for the electricity. Metal ladders, railings, diving boards, and the underground network of pipes and electrical wiring can conduct a strike that lands nearby. Lightning can strike the ground miles away, electrifying the pool and surrounding wet deck areas.
Determining When to Evacuate
Proactive evacuation is the only way to ensure safety and should begin before the storm is directly overhead. The “30/30 Rule” is a widely recognized safety guideline used to determine when a storm is dangerously close.
Use the flash-to-bang method by counting the seconds between seeing lightning and hearing thunder. Every five seconds indicates the storm is approximately one mile away. If the time between the flash and the bang is 30 seconds or less, you must evacuate the pool immediately.
When you hear thunder, you are within range of a lightning strike, and the pool should be cleared. Safe shelter must be sought in a substantial, fully enclosed building that has plumbing and wiring. Small, open structures like sheds, gazebos, or covered patios are not safe, and seeking shelter under an isolated tree is extremely dangerous. If a building is unavailable, a hard-topped, all-metal vehicle offers suitable protection.
Safety Protocols for Re-entry
The second part of the 30/30 Rule governs when it is safe to return to the water after evacuation. The pool area is not considered safe until 30 minutes after the last sound of thunder or the last observed flash of lightning.
This mandatory waiting period is necessary because lightning can strike miles away from the visible storm center. Even after the main storm has passed, a strike may occur up to 10 miles away from the storm’s core. Returning prematurely increases the risk of being struck by a bolt from the trailing edge of the storm.
Local weather alerts and the instructions of facility staff should be followed closely. Monitoring the weather for warnings from sources like the National Weather Service provides localized, up-to-date information on storm movement. Adhering to the 30-minute waiting period is the most effective safety protocol.