Lightning: stop play the moment it's seen or thunder is heard, and don't resume until 30 minutes have passed since the last flash or rumble — any new strike resets the clock. Heat: sports medicine guidance uses wet bulb globe temperature (WBGT), which factors in humidity, wind, and sun, not just air temperature, to decide when to modify or stop activity. Both are safety triggers an on-site official can act on directly, and both are handled like a weather rainout for billing — no charge if called before your official leaves home, a time-based fee if the delay happens after they've already arrived.
Two Different Weather Risks, Two Different Triggers
Coordinators tend to lump "bad weather" into one category, but lightning and heat are separate hazards with separate rules, and mixing them up is where policies get written wrong. Lightning is an immediate, binary danger — either conditions require a full stop or they don't, and the decision is made in seconds. Heat is a cumulative, graded risk that builds over the course of a practice or game, and the response scales from extra water breaks up through full cancellation depending on how hot and humid it actually is. A written policy that treats both the same way — "we'll call it if it looks bad" — leaves officials and coordinators guessing at the exact moment guessing is most dangerous.
The 30-30 Rule for Lightning
The lightning standard most school and youth sports programs reference comes from the NFHS Sports Medicine Advisory Committee: the moment lightning is seen or thunder is heard, activity stops immediately — not at the next timeout, not after one more play, not once players finish jogging off the field. Everyone evacuates to a designated safe structure or vehicle. Play doesn't resume until 30 minutes have elapsed since the last lightning flash or thunder was heard, and if a new flash or rumble happens inside that 30-minute window, the clock restarts from zero. A rolling thunderstorm that keeps producing strikes every 15-20 minutes can push a suspension well past an hour without ever technically being a full rainout.
Whether the rain has stopped is irrelevant to this decision — a clear sky with distant thunder still triggers a suspension, because the hazard is the lightning itself, not the precipitation. This is also why a lightning delay and a rain cancellation aren't the same event even though they often happen together; our rainout referee policy guide covers the standalone rain-and-flooding scenario in more detail, while this page is specifically about the lightning trigger.
Who Has Authority to Call It
Unlike a rainout, which is often a judgment call made jointly by a coordinator, league official, or facility, a lightning suspension isn't treated as optional once the trigger condition is met. Certified officials are generally trained to stop play on their own authority the instant they see a flash or hear thunder, without waiting for a sideline conversation. Town parks departments and school districts that hold their own field-closure authority reinforce this rather than override it — nobody in the chain has standing to tell an official to keep playing through active lightning. If you're staffing a facility that doesn't already have this written down, put it in writing before the season starts rather than leaving it as an unwritten assumption your officials are expected to guess at.
Heat: Why the Thermometer Isn't the Right Number
Sports medicine organizations — the NFHS Sports Medicine Advisory Committee, the American College of Sports Medicine, the National Athletic Trainers' Association, and the NCAA all point the same direction here — recommend wet bulb globe temperature (WBGT) over simple air temperature or even the standard heat index for deciding when to modify or stop outdoor activity. WBGT combines ambient temperature, humidity, wind speed, and radiant heat from direct sun into a single reading, because two afternoons that both show "90 degrees" on a phone can carry very different real exertional heat risk depending on how humid and sunny each one actually is.
| WBGT Reading | Typical Guidance |
|---|---|
| Below 80 | Normal activity, standard hydration breaks |
| 80 – 85.9 | Increase rest breaks, monitor closely for at-risk athletes |
| 86 – 89.9 | Limit activity to acclimatized, fit, lower-risk participants; distance events often cancelled |
| 90 and above | Cancel or delay outdoor exercise for all participants |
These bands come from published sports medicine guidance, not a Long Island-specific rule, and individual leagues and school districts set their own exact policy — some use a handheld WBGT meter on-site, others rely on the nearest reporting station. What doesn't change is the underlying idea: humidity and direct sun matter as much as the number on the thermometer, which is why "it's only 88 degrees" isn't, on its own, a reason to keep a tournament running through the hottest part of a humid August afternoon.
🌡️ August practices are the highest-risk window. Preseason conditioning often starts before players are heat-acclimatized, which is exactly when exertional heat illness risk is highest. Our preseason scrimmage referee guide covers the booking side of that specific stretch.
What Both of These Mean for a Referee Booking
Functionally, we treat lightning and heat suspensions the way we treat a weather rainout: timing relative to your official's travel is what determines whether there's a charge. Called or already in effect before your official leaves home, there's typically nothing to bill — the game hasn't started and nobody's time has been spent. Once an official is on-site and a game gets suspended mid-way, whether for a lightning hold or a heat-driven stoppage, their time already spent on your booking is the thing being compensated, not whether a final whistle blew. A 45-minute lightning hold that eventually clears and finishes the game is different from a full cancellation, and different again from a heat-driven decision to stop for the day — tell us which one happened and we'll sort out the right outcome rather than applying a blanket rule that doesn't fit.
Multi-field tournaments carry extra complexity here, since a lightning hold suspends every field at once — unlike a rainout, where only the low-lying fields might flood — while a heat-driven decision might affect some age groups or event types before others. Our tournament referees guide covers the broader staffing math for multi-field weekends; flag your event's outdoor exposure and expected conditions when you book so officials assigned to your fields know what threshold you're working from.
Building a Written Policy Your Officials Will Actually Follow
Leagues that avoid disputes during a summer heat wave or a rolling thunderstorm almost always have their threshold written down before the season starts, not improvised mid-tournament. A workable policy names who has authority to call a stop (and confirms officials can act on lightning without waiting for sign-off), states the specific trigger you're using for heat — a WBGT reading, a heat index number, or a simple "if it hits X degrees with humidity above Y" rule of thumb if you don't have measurement equipment on-site — and spells out what happens to a booking, a fee, and a makeup date once either trigger is hit. Publish it to your coaches, officials, and staffing service together, so nobody's finding out what the rule is for the first time in the middle of a 95-degree Saturday.
If your league runs mostly through summer tournament season, when both heat and afternoon thunderstorms are most likely to overlap, build the written policy into your season planning rather than your in-season improvising — it's a lot easier to agree on a threshold in March than to negotiate one while a storm cell is visible on radar and forty families are standing at the fence waiting for an answer.
Planning a Summer Tournament or August Practice Schedule?
Tell us your league's lightning and heat thresholds when you book, and we'll make sure the official assigned to your fields is working from the same rules you are.
Reach EmergencyRefs at EmergencyRefs.com →Frequently Asked Questions
Play stops immediately when lightning is seen or thunder is heard, and doesn't resume until 30 minutes have passed since the last flash or rumble. Any new lightning or thunder resets the 30-minute clock.
Generally yes — most certified officials are trained to stop play on their own authority the moment they see lightning, rather than waiting for a coordinator's approval.
Heat risk depends on humidity, wind, and sun as much as air temperature, which is why sports medicine guidance uses wet bulb globe temperature (WBGT) rather than a simple thermometer reading.
It's handled like our rainout policy: no charge if called before your official leaves home, a time-based fee if they're already on-site when play is suspended.
It isn't state law, but it's the standard most school and youth sports programs reference in their emergency action plans. Check your specific league or facility's written policy.