Swimming in an outdoor pool while it is raining presents a variety of risks, and the safety of the activity is highly conditional. The primary concern is the possibility of an accompanying thunderstorm, which introduces an immediate and severe electrical hazard. Beyond the threat of lightning, rain can destabilize the pool’s water chemistry and create physical dangers on the surrounding deck. Understanding these specific risks is necessary before deciding to stay in the water.
The Primary Hazard of Lightning and Thunderstorms
Lightning during a rainstorm transforms swimming into a serious safety risk. Water conducts electricity, and a strike to the pool or surrounding area transmits a powerful electrical charge through the water. This hazard is not limited to a direct strike, as the current can also travel through surrounding metal objects like plumbing, fences, and pool equipment.
An electrical charge can also be conducted through the ground, which is why seeking shelter in an open structure like a gazebo or pool house is insufficient during a storm. When thunder is heard, lightning is close enough to strike the area, even if the sky appears clear or the storm seems distant. Lightning has been known to strike up to 10 miles away from the center of a storm, a phenomenon sometimes called a “bolt from the blue.”
Safety experts recommend using the “30/30 Rule” to determine when to evacuate the water and when it is safe to return. The first “30” means that if the time between seeing a lightning flash and hearing the thunder is 30 seconds or less, the storm is approximately six miles away, and the pool must be evacuated immediately. The second “30” requires waiting at least 30 minutes after the last sound of thunder is heard before returning to the water, ensuring the storm has fully passed.
Impact of Rain on Pool Water Chemistry
Even a non-electrical rain event negatively affects the pool’s chemical balance, creating maintenance issues and health concerns. Rainwater is often slightly acidic due to dissolved atmospheric carbon dioxide, causing the pool’s overall pH and alkalinity levels to drop. A lower pH makes the water more corrosive, which can irritate swimmers’ skin and eyes and damage the pool’s plaster and metallic equipment.
The sheer volume of rainwater causes a chemical dilution effect, reducing the concentration of sanitizers like chlorine. A drop in chlorine effectiveness compromises the pool’s ability to kill bacteria and prevent algae growth. Contaminants like dust, pollen, and debris are washed into the pool from the air and surrounding surfaces, placing a higher demand on the remaining sanitizer.
Heavy rainfall dilutes the total alkalinity, a chemical buffer that stabilizes the pool’s pH. This makes the water chemistry more volatile and prone to rapid shifts. Pool owners should test chemical levels immediately after any significant rainfall to restore the balance.
Managing Physical Risks Around the Pool Deck
When rain is falling, several physical factors contribute to a heightened risk of injury. The most immediate danger is the creation of slippery surfaces on the pool deck and surrounding walkways. A wet deck increases the risk of a slip-and-fall accident, which can lead to serious head or body injuries.
Rain also significantly compromises visibility, affecting both swimmers and those supervising them. Reduced sightlines make it difficult for lifeguards or parents to spot a swimmer in distress, particularly if the water surface is agitated by heavy raindrops. This reduced visibility directly hinders the ability to respond quickly in an emergency.
Swimming in the rain, particularly when combined with wind, increases the risk of rapid body temperature drops. The combined effect of cold water, rain, and wind chill accelerates heat loss, increasing the potential for hypothermia or cold shock. Swimmers should monitor themselves for signs of excessive shivering or disorientation.