The short answer
Close and clear the water the moment lightning is seen or thunder is heard within roughly 10 km — a flash-to-bang count of 30 seconds or less. Send everyone to substantial shelter and keep the pool or beach closed until at least 30 minutes have passed with no new strike or thunderclap. Reopening requires a fresh check of radar and forecast, not just a running clock.
Key takeaways
- The trigger is the 30/30 rule: a flash-to-bang count of 30 seconds or less means the storm is about 10 km away and the area must close.
- Water conducts current, so swimmers near the surface and people on wet decks evacuate first, ahead of spectators and the beach.
- Beach closures are layered: drop patrol flags, announce, sweep the waterline and sand, then retire lifeguards to shelter.
- Only a substantial building or a metal-roofed vehicle counts as shelter; gazebos, tents, trees and pavilions do not protect.
- Stay closed for 30 minutes after the last flash or thunderclap because a typical storm moves about 20 km away in that time.
- An indoor pool may stay open only if its building is properly earthed and bonded per the lightning-protection standard and that is proven by testing.
- Assign a lookout, a single decision-maker and a communication chain, and log every closure in writing.
What actually triggers the decision
A thunderstorm turns an ordinary day at the water into an electrical hazard in seconds, because lightning can strike tens of kilometres ahead of the rain and water spreads current across its surface. That is why most aquatic facilities and lifesaving services worldwide converge on one threshold: the 30/30 rule, promoted by national weather services and rescue organisations.
The first 30 is about distance. Count the seconds between a lightning flash and the thunderclap; sound travels roughly one mile every five seconds, so a flash-to-bang count of about 30 seconds puts the storm about 10 km (6 miles) away — the point at which the decision is already made. Hearing thunder without seeing the flash is still a trigger, because the sound proves a discharge is close enough to be dangerous.
- Any audible thunder is a trigger, even if no flash is seen and rain has not arrived.
- A remote lightning detector alert or a severe-weather warning is a valid trigger — do not wait for the first crack.
- Do not wait for rain: lightning routinely strikes ahead of the rain shaft, so a dry sky is not proof of safety.
- When the flash-to-bang count exceeds 30 seconds, keep watching and brief the team, but do not open the water while activity builds.
Evacuation order: who leaves the water first
Priority goes to people in the water and on wet decking, who face the greatest danger because water conducts electricity and a ground strike spreads a current along the surface. A clear signal stops swimming first, then staff firmly but calmly walk everyone out of the basin, checking corners, ladders and dark spots before calling the area empty.
After the water, clear the deck, diving boards, lifeguard towers and open changing areas. Lifeguards and crew leave last, only after confirming the zone is empty. On open sites, tell guests not to run out of the facility during an active storm: sheltering inside is safer than walking across open ground.
- Stop swimming with one signal, reinforced by whistle, public-address announcement and hand signals.
- Sweep the basin: corners, ladders, dark patches near walls and lane lines.
- Clear the deck, walkways, towers and open changerooms.
- Remove metal objects from the deck: poles, umbrellas, chairs, flags and equipment.
- Assign one staff member to make the final sweep and confirm the area is empty.
Beaches are not pools: closure is layered
An open beach has no single building or fence, so closing it is a sequence of actions rather than one signal. When the flash-to-bang count reaches 30 seconds (storm about 10 km away), lifeguards drop the patrol and surf-craft boundary flags, announce the closure, and clear swimmers and beach users.
Because the space is open, some visitors resist or never hear a single announcement. A walking patrol along the waterline and across the sand reaches people individually far better than one loud call. Lifeguard towers and metal masts are themselves tall objects and a strike risk, so staff do not remain on them during active discharges.
- Drop the patrol and surf-craft boundary flags — the visible sign the beach is closed.
- Announce the closure over the PA and repeat it with a foot patrol.
- Clear swimmers, surfers and people in shallow water off the beach.
- Check shoreline showers, changing huts and shelters — they are not safe refuges.
- Advise the coordination desk and log the closure.
Shelter that actually protects
The only genuinely safe place from lightning is a substantial enclosed building that is earthed, or a metal-roofed vehicle. Everything else — gazebos, marquees, awnings, tents, trees and small sheds — only looks protective and can itself take the strike.
Lifesaving organisations stress that roughly one in four people struck by lightning were sheltering under a tree, so even a single tall tree is a spot to leave. Once inside, avoid touching metal, plumbing, showers and corded phones, because a charge can travel through pipes and wiring. If someone is caught in the open with no refuge, the safer move is to crouch in a low hollow with feet together and remove metal objects — not to lie flat or be the tallest object around.
- Substantial building or metal-roofed vehicle — yes, this is shelter.
- Gazebos, tents, trees, awnings and marquees — no, these do not protect.
- Do not use showers, taps or corded phones once inside.
- Put down umbrellas, poles and rods; remove metal jewellery from head and upper body.
- Stay clear of metal fences, power lines and flag masts.
The reopening countdown: why 30 minutes
The second 30 of the rule is time. The facility stays closed for at least 30 minutes after the last lightning flash or the last thunderclap, whichever comes later. The logic is simple: a typical thunderstorm moves at roughly 40 km/h, so in half an hour it travels about 20 km away, sharply reducing the chance of another strike.
Reopening is not decided by a timer alone. A named staff member must confirm that 30 minutes passed with no new flash or thunder and must check the radar picture and forecast. Storms can double back, and lightning fires from the back edge of a cloud as readily as from the front, so reopening too early is one of the most common and dangerous mistakes.
- Start the 30-minute count after the last flash or thunderclap — whichever is later.
- Assign one person to watch the clock and own the count.
- Before reopening, check the forecast and radar to confirm the front is not returning.
- Reopen in stages: staff first, then guests and swimming.
- Record the closing and reopening times in the log for review and insurance.
Indoor pools: the exception that must be proven
Indoor pools sit in a genuine debate: there are no known lightning incidents causing electrical injury to users of indoor aquatic facilities, so for years the industry practice was to evacuate only outdoor basins. Current lightning-protection standards now advise treating indoor and outdoor pools the same — with one important qualification.
If an indoor pool sits inside a substantial building that is earthed and bonded as part of its construction, the building itself acts as a lightning-protection system, and evacuation is not required — provided testing confirms the structure meets the relevant standard (such as AS/NZS 1768 in Australia). Without that proof, the conservative approach is to apply the outdoor protocol to the indoor basin as well. Write the position into your facility manual and agree it with the owner or certifying engineer.
- Confirm the building has a working lightning-protection system and a record of bonding tests.
- Without proof of earthing, treat the indoor pool exactly like an outdoor one.
- Document your indoor-pool position in the manual and have it signed off.
- Train staff on the difference: untested indoor pools close, tested indoor pools may operate.
Roles, communication and pre-season drills
A protocol works when roles are fixed before the season: one person is the weather lookout watching the forecast, radar and detector; one person owns the closure decision so there is no argument over who blows the first whistle; and there is a notification chain for guests and staff, with a backup channel in case the PA fails.
The team should rehearse evacuation on deck, not just read the manual: walk the routes to shelter, confirm there is enough shelter for the headcount, and debrief afterwards. Crew must understand why they themselves must come off the water and the towers even if guests resist, and how to enforce the rule patiently but firmly.
- Write a diagram of who decides, who watches the weather and who announces.
- Map every verified shelter and route onto a plan of the facility and grounds.
- Run at least one full evacuation drill before the peak season.
- Back up the notification system: PA, whistle, radio and a loudhailer.
- Keep a storm log: time of closure, reason, time of reopening and the name of the decision-maker.
Put it into practice
Clear-the-Water Staff Decision Card
Print this card and keep it at the control point and in the duty log. It converts the 30/30 rule into concrete steps so any shift follows the same sequence, without improvisation or argument during a fast-moving storm.
- Before shift: check the forecast and warnings; confirm the lightning detector and PA are working.
- Trigger: if you see a flash or hear thunder, count flash-to-bang; 30 seconds or less means the storm is about 10 km away.
- Decision: the named authority announces closure of the swimming zone with one clear signal.
- Water: stop swimming, clear everyone from the basin, and visually check corners, ladders and the floor.
- Deck and beach: clear decks, walkways, towers and changerooms; remove loose metal objects.
- Shelter: direct guests and staff to a substantial building or metal-roofed vehicle; gazebos and trees are excluded.
- Staff: lifeguards leave the towers last and keep watch from inside the shelter.
- Timer: 30 minutes from the last flash or thunderclap, whichever is later, watched by one person.
- Reopen: re-check radar and forecast, then reopen in stages, starting with staff.
- Log: record time of closure, reason, time of reopening and the decision-maker's name.
Questions people ask
Can a pool reopen 30 minutes after the last thunder even if storm clouds are still visible?
The 30/30 rule permits reopening 30 minutes after the last flash or thunderclap, but that is a minimum, not an automatic green light. A named staff member must confirm no new strikes occurred in that window and check the radar and forecast for a returning front. If the storm is still near or moving toward the site, waiting longer is the safer call.
Why is being in water dangerous during a storm if the lightning did not hit the pool directly?
Water conducts electricity well, and a strike to ground or water nearby spreads current across the surface and through pipes and wiring connected to the basin. A swimmer near the surface can be affected by step voltage even metres from the point of impact. That is why clearing the water is the first priority in any lightning protocol.
Should an indoor pool close during a thunderstorm?
Not necessarily. If the building is substantial, earthed and bonded per the lightning-protection standard and testing proves it, the structure itself acts as lightning protection and the pool can remain open. Without that proof, the conservative approach is to treat the indoor basin like an outdoor one. Document the decision in your facility manual.
What should staff do if a guest refuses to leave the water when a storm is announced?
Repeat the warning in person and explain the risk of electrical current in the water. If the guest still refuses, staff should not get into a physical confrontation — staying on the deck during active discharges puts them in greater danger. They leave the zone, log the incident, and call security or police from a safe location if needed.
Which shelters on a beach are actually safe from lightning?
Only a substantial enclosed building and a metal-roofed vehicle qualify as safe. Beach canopies, umbrellas, marquees, tents and trees do not protect and can themselves be struck; rescue services report that about one in four lightning victims had sheltered under a tree. Inside shelter, avoid showers, taps and corded phones.
Sources and further reading
Sources were checked when this page was generated. Confirm changing dates, rules and prices with the original publisher.
- Lightning Safety Tips and Resources — U.S. National Weather ServiceU.S. National Weather Service (NOAA)
- Outdoor Activities: Lightning Safety and Preparedness — National Weather ServiceU.S. National Weather Service (NOAA)
- SV31 — Supervision During Thunderstorms (Lightning), Royal Life Saving SocietyRoyal Life Saving Society (WA)
- 9.6 Lightning — Standard Operating Procedures, Surf Life Saving South AustraliaSurf Life Saving South Australia
- PSS 8.6 Lightning — Public Safety Standard Operating Procedures, Surf Life Saving NSWSurf Life Saving NSW
- How Dangerous is Lightning to Swimmers? — Loss Control (National Lightning Safety Institute guidance)Great American Insurance Group
- Clarification on Indoor Aquatic Facilities and Lightning SafetyLeisure Institute of Western Australian Aquatics (LIWA)