Part of getting the most out of swimming is having full knowledge of water safety, which includes proper procedures for inclement weather, especially during rain and storms. The simple rule is from the National Lightning Safety Institute is, "If you can see it, flee it; if you can hear it, clear it." This means that though rain itself does not necessarily pose a safety threat to swimmers, thunder and lightning can develop quickly and cause a risk. Consult with the lifeguard at your pool or beach before entering the water when it is raining.
Lightning can just as easily strike something connected to the pool, such as a water pipe, as the pool itself, which means that both indoor and outdoor pools should be avoided during a storm that contains thunder and lightning. Return to the pool only when you have not heard any thunder for at least 30 minutes.
Strong winds can affect the water conditions and currents, especially in oceans. Heavy rain can hamper your visibility of the shoreline, causing you to become disoriented. Additionally, rains can cause bacteria and other harmful matter to be washed into the ocean and waterways; therefore, swimming should be avoided during and for 12 to 24 hours following heavy storms.