Extreme heat school closure and early release messages
Heat closures are growing fastest in districts whose buildings were never designed to be cooled. Ten variants, a heat-index action table, and honest wording for the families whose homes are also without air conditioning.
| Heat index | Outdoor recess | PE outdoors | Athletic practice | Water breaks | Equipment |
|---|---|---|---|---|---|
| Below 80°F | Normal | Normal | Normal | Available on request | Full |
| 80–90°F | Normal, shade offered | Normal | Normal, monitor | Every 30 min | Full |
| 90–95°F | Shortened | Shortened, shade | Shortened, no doubles | Every 20 min | Helmets off when not active |
| 95–99°F | 15 min max | Move indoors | 1 hour max, no pads | Every 15 min, mandatory | No pads |
| 100–104°F | Indoors | Indoors | Light activity only, no contact | Continuous access | Shirts and shorts |
| Above 104°F | Indoors | Indoors | Cancelled | n/a | n/a |
Bands follow the general shape of state athletic-association heat policies, several of which now use wet bulb globe temperature (WBGT) rather than heat index because WBGT accounts for radiant load and surface type. If your state association publishes WBGT thresholds, use theirs — this table is a starting point for districts that have nothing written down, not a substitute for a governing body's policy.
The ten variants
1. Full closure for heat, buildings without air conditioning
[District] schools are CLOSED [today/tomorrow], [date], because of extreme heat. Forecast highs of [value] with a heat index of [value] leave classrooms in our un-air-conditioned buildings above safe teaching temperatures by mid-morning. [Building] is open as a cooling centre from [time]. — [Name], Superintendent
2. Heat-shortened day
[District] will dismiss at [time] today and tomorrow because of extreme heat. Buses run on that schedule. Dismissing before the hottest part of the afternoon lets us hold a full morning of instruction in buildings that are still comfortable. After-school activities are cancelled.
3. Partial closure — the schools without AC only
[School] and [School] are CLOSED [today] because of heat; those buildings do not have air conditioning. All other [District] schools are open on the normal schedule and are cooled. Families at the closed schools: today is excused for all students.
4. School open, all outdoor activity suspended
School is open on the normal schedule. With a heat index forecast at [value], all recess and PE are indoors today and students will not be outside except to board buses. Please send a filled water bottle.
5. Athletics cancelled, school unaffected
School runs normally today. All outdoor athletic practices and this evening's [contest] are [cancelled/moved to [time]] because the heat index will exceed [value] during the practice window. Indoor practices continue.
6. Practice moved to early morning
Outdoor practices this week move to [time] to [time] in the morning. Afternoon practice is suspended while the heat advisory holds. Please send athletes with two filled bottles; water and ice are provided at all sites.
7. Heat advisory with a bus note
School is open. Buses are not air conditioned and interior temperatures can exceed outside temperature significantly. Windows and roof hatches will be open, drivers will run with reduced dwell time at stops, and water is available on arrival at every school.
8. Heat with a medical-sensitivity note
School is open with all activity indoors. If your child has asthma, a heart condition, or takes medication that affects temperature regulation, please make sure the school nurse has current information. Students with heat-related accommodations in an IEP or 504 will have them applied today without you needing to ask.
9. Second consecutive heat closure
Schools remain CLOSED for a second day because of heat. Buildings that were still holding temperature yesterday morning did not cool overnight, which is what makes consecutive heat days worse rather than better. Cooling centre at [building] from [time]. Next update by [time].
10. Heat wave breaking, reopening
Schools REOPEN tomorrow on the normal schedule. Overnight temperatures dropped enough for buildings to shed heat and classrooms will start the day in range. Outdoor activity remains suspended until the heat index falls below [value].
SMS, voice and Spanish
[District]: CLOSED [date] for extreme heat. Classrooms in our buildings without AC exceed safe temps by mid-morning. Cooling centre at [site] from [time]. — 152 characters.
[District]: Open today, but all recess and PE indoors, heat index [value]. Please send a full water bottle. Outdoor practice cancelled. — 130 characters.
[District]: Dismissing at [time] today and tomorrow for heat. Buses run early. No after-school. Full morning of class as normal. — 122 characters.
60-second voice script. "This is a message from [District Name] Public Schools. Because of extreme heat, all [District] schools will be closed [day], [date]. Temperatures are forecast to reach [value] with a heat index of [value]. Several of our buildings do not have air conditioning, and classrooms in those buildings rise above safe teaching temperatures by mid-morning. All after-school activities and athletic practices are cancelled. [Building] is open as a cooling centre from [time] to [time], and meals are available there. If anyone in your household needs help getting to it, please call [number]. We will send an update about [next day] by four o'clock. Thank you. This message is from [District Name] Public Schools."
Cierre por calor extremo: Las escuelas del [Distrito] estarán CERRADAS el [fecha] por calor extremo. Se pronostican temperaturas de [valor] con una sensación térmica de [valor]. Varios de nuestros edificios no tienen aire acondicionado y las aulas superan la temperatura segura antes del mediodía. [Edificio] estará abierto como centro de enfriamiento de [hora] a [hora], con comidas disponibles.
The buildings decide this, not the forecast
A heat closure is fundamentally a facilities decision wearing a weather costume. Two districts under the same heat dome will make opposite calls, and the difference is almost always the building stock.
The conditions that force a decision even when the outdoor index looks survivable:
- Classrooms without mechanical cooling in buildings with single-glazed windows and dark roofs, which climb through the morning and do not shed heat overnight during a multi-day event. Day three is worse than day one.
- Portable classrooms, which heat faster than the main building and often have the weakest cooling.
- Gyms and cafeterias with high ceilings and no cooling, which become unusable well before classrooms do — and which are where you would otherwise put an indoor recess.
- Upper floors, which in a three-storey building can run several degrees above the ground floor with the same system.
- Kitchens, which add substantial heat load to the building they sit in and often force a shortened-day decision before classrooms do.
Do not tell families to keep children home if they are uncomfortable. It sounds compassionate and it is a serious equity problem: the households most likely to lack cooling at home are the ones most likely to take the offer, and school — even a warm school — is often the cooler and safer environment. Either the building is fit to occupy or it is not. If it is not, close it for everyone. If it is, say so and describe what you are doing to make the day work.
Sending it during a heat event
Heat events differ from storms in one important way: they last for days and the decision changes daily. That makes cadence the design problem rather than speed.
Set an update time and hold it. A district that sends at 4pm every afternoon for the duration of a heat advisory — even when the message is "tomorrow is unchanged" — gets far fewer calls than one that sends only when something changes, because families cannot distinguish "nothing has changed" from "they have not decided".
Practically, that is a scheduled send each afternoon. Kastr resolves the audience at the moment the message fires rather than when you queued it, so a week of scheduled 4pm updates reflects roster changes as they happen. The composer shows a live per-channel cost estimate, which matters when you are sending daily for a week: five district-wide voice calls cost real money and email costs essentially nothing, so a daily email with SMS reserved for actual changes is usually the right shape.
Translation preview is worth using here. Heat guidance carries specific instructions — hydration, medication sensitivity, cooling-centre hours — where a mistranslation has consequences. Kastr renders the draft through DeepL in the languages you send in so you can read it before it goes, rather than after.
The honest caveat, same as everywhere in this cluster: variant 3 closes two named schools and keeps the rest open, and Kastr's audience resolution does not do building-level targeting yet. It resolves named individuals and everyone. A partial closure today means building an explicit audience, which is workable at one school and painful at ten.
Questions people actually ask
At what temperature or heat index do schools close?
There is no national threshold and most districts do not publish one, which is part of why the question is asked so often. In practice the trigger is a combination of forecast heat index and building capability: a district with cooling throughout rarely closes at all, while a district with un-air-conditioned buildings often makes the call somewhere around a forecast heat index in the high nineties, earlier on the second or third consecutive day.
Can a school stay open with no air conditioning during a heat wave?
Often yes on day one, less often by day three, because buildings that cannot shed heat overnight start each successive morning warmer. Common mitigations are a shortened day that ends before the afternoon peak, all activity indoors on the cooler ground floor, fans and open circulation where the outside air is cooler than the interior, and relocating classes out of portables and upper floors.
Should athletics and outdoor practice be cancelled before school is?
Almost always, and by a wide margin. Sustained exertion in the heat is a far higher risk than sitting in a warm classroom, and most state athletic associations publish binding heat thresholds that will make the decision for you. Moving practice to early morning is usually a better answer than cancelling outright.
What is the difference between a heat closure and a heat-shortened day?
A shortened day holds a full morning of instruction and dismisses before the afternoon peak, which frequently still clears the state's daily instructional-minute minimum and therefore does not create a make-up day. A closure does not. Where the buildings are tolerable until early afternoon, the shortened day is usually the better trade — but check your daily minimum before assuming it counts.
How do you word a heat message for families whose homes are also without AC?
Name a cooling centre with real hours and meals, and give a phone number for families who cannot get there. Do not frame staying home as the safer option, because for many families it is not. If you are closing, close for everyone and be direct that the building is the problem.
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