Lightning and swimming pools: when to get out and when to go back
Updated · 5 min read
Leave the water as soon as you hear thunder, indoor pools included. Water conducts current across a wide area, and a swimmer is the tallest object on a flat surface. Wait 30 minutes after the last thunder before returning.
Why is water so dangerous during a thunderstorm?[1][2]
Two reasons compound each other. A swimmer's head is the highest point on an otherwise flat surface, and water spreads current outward from the strike point across a wide area. A strike does not have to hit you to reach you.
Lightning that hits open water discharges mostly across the surface rather than sinking into it. That is worse for swimmers, not better, because the current stays in the layer where people are. The affected radius is far larger than the strike itself.
Natural water bodies add dissolved salts and minerals, which conduct better than a treated pool. Ocean and lake strikes carry current further from the entry point than the equivalent flash into a chlorinated pool.
Are indoor pools safe during a storm?[1]
Safer, but not exempt. An indoor pool sits inside a building with plumbing and metal structure, and that is the same conduction path that makes showering risky. Most aquatic safety guidance clears the water for lightning regardless of whether the pool is covered.
The building shell helps in the way any substantial building helps: it gives current a route around the occupants. What it does not do is isolate a large body of water that is connected to metal pipework, ladders, rails and pumps.
Public facilities generally clear indoor pools on thunder anyway, which tells you how the people carrying the liability read the risk. It is a 30-minute interruption against a small chance of a serious injury.
How long do you have to wait to swim again?[1]
Thirty minutes after the last thunder, the same rule that applies to every other outdoor activity. Storms produce strikes well beyond their rain, so a pool under clear sky can still be within reach of a storm that has moved on.
Pools are where this rule gets broken most often, because the interruption is so unwelcome and the sky usually looks fine by then. The 30 minutes is not a formality. It covers exactly the window in which the storm is departing and still throwing strikes behind it.
What about hot tubs, splash pads and beaches?[1]
Treat them the same way. A hot tub combines water, metal plumbing and mains-powered equipment, which is the worst combination indoors or out. Beaches are flat, open and often the tallest-object problem in its purest form.
- Hot tubs
- Water plus wired pumps and heaters. Get out on thunder, indoors or outdoors
- Splash pads
- Shallow, but the plumbing and the open ground around them are the real issue
- Beaches
- Flat and exposed. Head for a building or a hard-topped car, not a beach umbrella
- Lakes and rivers
- Get off the water first, then get away from the shoreline
References
- Lightning SafetyUS National Weather Service, 2026
- Five Ways Lightning Strikes PeopleUS National Weather Service, 2026
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- What to do if you are caught outside in a thunderstormNo safe place exists outdoors. Here is what the NWS actually recommends, why crouching was dropped from the advice, and how to pick the least bad option.
- Lightning safety and the 30-30 ruleIf thunder follows lightning within 30 seconds, go indoors and stay there 30 minutes after the last thunder. Learn why both numbers matter.
- What to do if a thunderstorm catches you on a boatA boat is often the tallest object for miles. What to do when a storm builds while you are on the water, and why the mast changes everything.
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