Lightning Safety and Indoor Pools: To Clear or Not to Clear

May 1, 2016, Department, by National Recreation and Park Association

Clearing Indoor Pools Presents Greater Risks

By Dr. Tom Griffiths, Ph.D. and Rachel Griffiths, MA

If our goal was to eliminate all risks, we would drain swimming pools and close them to the public. Recreational waters are inherently risky. With the best policies, procedures and supervision, swimming pool patrons face risks such as drownings, broken necks, slips and falls, and electrocutions. Our mission, as Aquatic Risk Managers, is to reduce and warn against potential risks. 

Since it started tracking fatal electrocutions in swimming pools and spas, the U.S. Consumer Product Safety Commission has reported a total of 74 electrocutions between 1990 and 2014. None have been caused by lightning strikes. The majority of electrocutions in swimming pools have been caused by underwater lights, pool pumps, filters, vacuums, electrical outlets and switches, extension cords and others. We know electricity and water do not mix, but we continue to keep pools open with electricity driving their disinfection, circulation and filtration 24/7, even though there is an electrocution risk. However, when electrical storms approach, too many close their indoor swimming pools. 

There are no documented reports of fatal lightning strikes at indoor swimming pools. None! Ever! Ninety-five percent of all fatal lightning strikes occur outdoors, not indoors. The decision to close indoor swimming pools during these storms is based on irrational fears rather than objective facts. The problem with closing indoor swimming pools during electrical storms is that this policy places people at greater risk by removing them from the safe confines of swimming pools and placing them in unprotected areas like on phones, in showers, outdoors and in cars where electrical storms have killed people.

As Aquatic Risk Managers, we must prioritize real risks and de-emphasize perceived risks. We don’t believe the rationale: “If there is any risk at all, we will err on the side of safety.” Do we let our teenagers drive cars? Statistically speaking, that’s a real risk.

To us, lightning strikes are akin to shark attacks. Although both catastrophes are relatively rare, when they do occur, sensational headlines and videos are quick to appear on the mainstream and social media networks. Even with shark attacks, people don’t stop swimming in the ocean, and you’ve never seen or heard of a lightning strike killing someone in an indoor pool. Data drives good decisions and there is no data supporting closure of indoor swimming pools during electrical storms. 


Tom Griffiths, Ph.D., is President and Founder of Aquatic Safety Research Group, LLC. Rachel Griffiths, MA, is Communication Director for Aquatic Safety Research Group.


Risk Is Greater than Inconvenience

By Carl Swanson III and Steven E. Clark

Many inconsistencies and misconceptions exist regarding the lightning safety protocol for indoor swimming pools. Pool operators may assume patrons are safer from the elements in an indoor pool because it is indoors. This is not necessarily the case. Some examples of inconsistent protocol are:

  1. Patrons are evacuated only when lightning is 2 miles away and closing.

  2. Patrons are allowed back in the pool when 10 seconds have elapsed after the sound of thunder.

  3. Some agencies do not evacuate their indoor pools at all.

  4. Some agencies vacillate between evacuating and not evacuating the pool.

When metal parts of the pool are not connected to the building’s grounded metal components, Dr. Martin Uman, a professor and former chair of the University of Florida’s Department of Electrical and Computer Engineering, explains: “…there will be a voltage between them that could cause a shock….Electrical wiring to the pool lights or other electricity in or near the pool can also be problematic in the event of a lightning strike to the building. If the building is not properly lightning protected, the risks are higher.”

The National Electrical Code (NFPA 70) requires swimming pools and their buildings to be properly bonded and grounded; however, “grounding a pool cannot itself control lightning behavior to the electrical circuitry, nor to adjacent metallic conductors.”  In addition, electrical bonding of pools is, on rare occasions, improperly done and the bonding can deteriorate over time.

The National Weather Service, National Lightning Safety Institute and the National Athletic Trainers’ Association are three of several groups that recommend evacuation of indoor pools when the threat of lightning exists. Following are some practical suggestions when developing a lightning safety protocol:

  • Educate patrons and employees about the hazards of lightning (including pool safety).
  • Work with your maintenance/engineering staff to learn how your pool is connected to your plumbing and electrical systems. Understand the actual hazard!
  • Establish protocol with an action plan for your facility. This should include avoiding contact with all plumbing and electrical systems, as well as metallic structural components during a storm. Post the policy and educate your employees.
  • If you evacuate, encourage patrons to “shelter in place” in your facility. Discourage them from exiting your building into an active storm.
  • If you choose not to evacuate, consider advising patrons of the possible hazard so they have the option to take individual action.
  • Consult the National Weather Service for published guidelines for the timing of lightning safety.

We have not found a single lightning researcher who endorses staying in a pool, indoor or outdoor, in an electrical storm. Remember, absolute protection from lightning is impossible. We believe the risk of electrical shock from lightning is greater than the inconvenience of evacuating the pool. 


Carl Swanson, III, is a member of the Lightning Data Center since 1997, a storm chaser, lightning photographer and member of the National Weather Service’s spotter network. Steven E. Clark is a member of the Lightning Data Center and owner of Clark Consulting.


References in support of clearing indoor pools during lightning storms:

  1. Uman, Martin, Personal Communication, November 9, 2015.

  2. As cited from:  Kithil, Richard. “Lightning Safety for People at Swimming Pools Revised and Updated December 2015.”  National Lightning Safety Institute. 

  3. National Weather Service: "Lightning Safety – An Update.”  

  4. National Athletic Trainers’ Association, Inc.: “National Athletic Trainers’ Association Position Statement:  Lightning Safety for Athletics and Recreation.”  Journal of Athletic Training, 2013; 48(2): 258-270.  

  5. National Weather Service: “Lightning Safety and Outdoor Sports Activities.”