Snow Day Calculator: Will School Be Closed Tomorrow?

What is a snow day calculator?

A snow day calculator estimates how likely it is that school will close because of winter weather. It weighs the things a superintendent weighs before dawn — how much snow falls, whether it is still coming down at bus time, ice on the roads, how cold it is at the bus stop — and turns them into a percentage.

People call the same tool a snow day predictor, a school snow day calculator or a snow day probability calculator. This one is a manual weather calculator: you enter the conditions from your local forecast, and it calculates from exactly those figures. It does not fetch live weather or school closure announcements, and it never asks where you are. That makes it transparent — you can see every number it used — and it makes “what if the storm is two inches bigger?” one tap away.

How to use it

1. Pick the weather condition in your forecast — snow, heavy snow, freezing rain, sleet or mixed, extreme cold and so on. It fills typical figures and sets the scene; every figure stays editable.
2. Enter your forecast. Snowfall amount and how long it snows (or the rate), any rain or freezing rain, the temperature at bus time, the wind and gusts, and visibility. Leave the wind chill blank and it is worked out for you.
3. Place the storm on the timeline — evening, overnight, early morning, the school commute or school hours — and describe the roads you expect.
4. Describe your school: how easily it closes, city or rural roads, how sensitive the commute is.

The result updates as you type. It is a live calculation, not live weather: the page recalculates from your figures, it does not look anything up. Pick a weather type at the top to fill in typical numbers, then change them to match your own forecast.

Reading the result

You get three chances that add up to 100%: snow day, delay or early dismissal, and normal school day. Above them, the dashboard repeats the conditions you entered, so a screenshot always shows what the estimate was based on.

Factor breakdown shows each factor’s points as a bar and the total weather pressure on a 0–100 scale, with the points where a delay and a closure become more likely than not. Why did my result change? lists every factor that moved when you changed a value — for example “Snowfall (12 cm effective): +22 points” — and a dashed outline shows where each bar was before. Show your work gives the whole calculation, step by step.

The panel at the top follows your figures: falling snow for snow, heavier and faster for more of it, rain streaks for rain, ice crystals and frosted edges for freezing rain, cold mist for a bitter wind chill, and flakes that drift sideways as you raise the wind. It is a picture of the conditions you entered, not a forecast. With “reduce motion” turned on in your device settings it stays still.

Snow day prediction calculator vs snow day predictor

People search for a snow day calculator, a snow day predictor or a snow day prediction calculator, and they usually mean the same thing: “given this forecast, how likely is a snow day?” Some websites look up a forecast for your ZIP code; this one does not. It is a manual prediction tool: you enter the forecast you already have — from the National Weather Service, a local station or an app — and the Snow Day Prediction box shows a primary scenario (closure, late start, early dismissal or normal), a secondary scenario when another outcome is close behind, a scenario index out of 100 and a “Why?” table with each factor’s value, status and contribution.

“Prediction” here means the model’s output for the conditions you typed — it does not use live weather or a location lookup, and it is not an official prediction. Because nothing is fetched, it works the same in any winter and lets you test “what if” forecasts that no live tool can.

Delay vs closure: the four school-day outcomes

The model gives two curves from the same weather pressure: one for a full closure and one, set 14 points lower, for any disruption. The space between them is the in-between outcome — a late start or an early dismissal — and storm timing splits it. The Delay vs closure tool shows the result as a ladder:

1. Normal — roads are manageable at bus time.
2. Late start — the storm is over, or ending, before school, and a few extra hours of plowing and daylight would be enough.
3. Early dismissal — snow or ice arrives during school hours, so the risk is the trip home.
4. Closure — heavy snow or ice is still falling at bus time, or the totals are too large to clear.

Your current position is highlighted, and the tool tests the snowfall around your forecast to say how much more (or less) snow would change the primary scenario. Conditions often overlap — a storm can make both a late start and a closure plausible — so the result lists a secondary scenario instead of forcing a single answer. The four numbers are an estimated scenario probability: a documented heuristic from your inputs, not a measured historical rate and never a school decision.

Late start and the 2-hour delay

A late start buys time: crews keep plowing, salt starts working and the sun comes up. The Late start / 2-hour delay tool compares a normal start, a 1-hour delay, a 2-hour delay or a custom delay window with a theoretical “roads ready” time — the storm end time from the timing tool plus a clearing time that grows with the snow depth (and with ice), shortened when roads are treated. For each option it says whether the roads are estimated ready when that morning commute starts, whether snow is still falling, and how long a delay this scenario would need.

Overnight and pre-dawn snow that ends a few hours before school is the classic delay pattern; snow still falling at bus time usually is not solved by a delay. A “2-hour delay” is only a scenario option here: districts use different delay lengths, and some never delay at all. The clearing times are assumptions you can see, not a road-crew schedule.

Early dismissal scenarios

Some storms arrive after the buses have run. The Early dismissal tool gives an Early Dismissal Pressure level — low, moderate, high or very high — from the parts of your forecast that matter for the trip home: snow that starts during school hours, a peak near dismissal or the afternoon commute, conditions forecast to worsen through the afternoon, the snowfall rate, freezing rain, road deterioration and visibility. It uses the clock times from the timing tool, so enter the storm start, peak and the school end time there.

It is a pressure level, not a prediction that school will dismiss early. Districts weigh the same storm differently — some prefer to keep students until buses can run normally — and only their announcement counts.

Storm timing and snowfall timing

The same 6 inches mean very different mornings. Snow that ends at 10 p.m. can be plowed before buses run; snow that peaks at 6 a.m. lands on the commute. The Storm & snowfall timing tool takes clock times — when light snow starts, when heavy snow starts, the peak, the end, and the school start and end times — or up to 8 time blocks, each with its own snow, ice and temperature.

It places them on a timeline — evening, overnight, pre-dawn, morning commute, school hours, afternoon dismissal and evening return — and lists every overlap with the morning bus window (from 75 minutes before school), the school day and the afternoon bus window, for example “Heavy snow overlaps the morning bus window”. The window holding the peak sets the storm timing the estimate uses; press “Use this timing in the calculator” to apply it. The late-start, early-dismissal and morning-commute tools reuse the same timeline.

Road conditions and road treatment

Roads are scored from your description: dry, wet, slushy, snow-covered, icy or severely impaired (blowing snow, near whiteout). The Roads, treatment & visibility tool adds what crews have done — untreated, partially treated, recently treated or well treated — with the time since treatment, and the plowing progress at bus time.

Treatment lowers the road pressure, but less in deep cold (salt works poorly well below freezing), less as it ages, less under heavy snowfall and less on a thick glaze of ice. Plowing progress can add a little (not started by bus time) or take some away (main routes cleared). Neither ever lowers the road pressure below zero. Every weight is a documented assumption in the configuration, not a measured road-safety figure.

Visibility and school transportation

Visibility is entered two ways. The calculator itself uses a visibility setting — good, reduced, poor or very poor — that counts only when snow or ice is in play. The visibility check in the roads tool takes a physical distance in miles, kilometres or metres, with the snow intensity and precipitation type, and shows the visibility condition and its effect on school transportation, plus notes for blowing snow, heavy snow or freezing rain.

The distance stays separate from the estimate until you press “Use this visibility in the calculator”, so a measured value never silently changes the heuristic model. The National Weather Service publishes visibility in its forecasts and warnings; use those figures where you have them.

School bus route risk

Districts often close because buses cannot run safely, even when cars manage. The School bus risk tool scores how exposed your routes are: how many students ride, a city, suburban, rural or mountain setting, hills and grades, the longest route and ride, and the share of route roads still untreated — plus a share of the snow, ice, visibility and road pressure. Tick the box to let routes add a small, capped number of points to the estimate (at most 8). It is informational — not a transportation safety assessment and not an official bus decision.

Morning commute risk

The Morning commute tool follows one trip — a parent’s drive, a teacher’s commute or a student driver — from its departure time and travel time: departure → worst conditions → arrival, using the storm times from the timing tool. Each point says whether snow is falling, heavy or at its peak, or whether the roads are still being cleared after the storm.

A disruption level is added from the distance, travel time and route type, the weather and road pressure, the storm timing, and any road treatment or plowing progress you set. It does not change the school estimate and is not a road-safety rating.

District policy, regional thresholds and snow days used

There is no national rule for how much snow closes schools. Instead of a database of districts that would go out of date, the Policy, region & days used tool offers generic profiles that move the closure threshold:

• District policy profile: custom, lower-threshold, typical or higher-threshold. “Custom” lets you set your own threshold adjustment between −25 and 25 points.
• Regional scenario profile: lower, typical or higher snow tolerance — places where snow is rare tend to close for less. These are scenario assumptions, never a claim that a state, province or city closes at a set amount.
• Snow Days Used: optional and off by default. Choose 0–5, 6 or more, or a custom number. Districts have different snow-day budgets (or none), and some grow reluctant once their built-in days are used; if you pick the heuristic, the effect is small.

All three are scenario assumptions, not any district’s official policy or snow-day budget. Your district’s announcement is always the answer.

Plowing scenario

How long would it take to clear the roads that matter? The Plowing scenario uses plain arithmetic: passes needed for the snow depth (one pass per 10 cm), a working speed that drops in deeper snow and while snow is still falling fast (or your own clearing capacity per plow), the road length, the number of plows and the start time after a treatment delay. It reports the theoretical clearing time, when it would finish, how much would still be uncleared when the morning commute starts, and whether plowing would still be running at the school start time.

It is a theoretical estimate based on your assumptions — real crews prioritise main roads, refuel and work around traffic — and is not a municipal estimate.

What-if comparisons and cancellation scenarios

Forecasts change. The What-if comparison keeps your forecast as scenario A and lets you set up B (and C) by hand, or with quick presets: snowfall +2 or −2 inches, 10 °F colder or 5 °F warmer, the storm moving into the morning or after school, added freezing rain, better road treatment, delayed plowing or worse visibility. Presets stack, so you can build a cancellation scenario step by step.

The table shows each scenario’s primary outcome, the closure, delay, early-dismissal and normal chances, the weather pressure and the storm timing. Under it, What changed? traces each scenario back to A: the input change (for example snowfall 4 in → 8 in, storm timing overnight → morning), the factor change in points, and the outcome change (for example late start scenario → closure scenario).

The model, in the open

There is no public dataset that pairs forecasts with the closure decisions of thousands of districts, so no one can honestly fit a “scientific” snow day formula to it. The weights below are heuristic: reasoned assumptions, written down so you can see them, and the ones that matter most are yours to set.

The factors combine like independent risks: pressure = 100 × (1 − (1 − snow/100)(1 − ice/100)(1 − cold/100)(1 − extras/100)). Two moderate factors therefore add up to more than either alone, but never past 100.

The snow day chance is an S-curve centred on a pressure of 55: at 55 it is 50%, and the curve’s scale is 7 points. “Rarely closes” moves the centre up by 10, “closes easily” down by 10; rural bus routes move it down by 5 and city schools up by 4; a sensitive commute moves it down by 4; a boarding school moves it up by 20. The chance of any disruption (closure or delay) uses a centre 14 lower. The snow day chance is capped at 95%, because conditions can never make a closure certain. There is no random part: the same figures and settings always give the same answer.

Worked examples

• Snow at bus time. 10 cm (about 4 in) over 6 hours, still falling during the morning commute, −5 °C, 15 km/h wind, reduced visibility, snow-covered roads: weather pressure 58, and for a typical suburban public school a 61% snow day chance, 31% delay and 8% normal day.
• A big overnight storm. 20 cm (about 8 in) overnight at −6 °C with snow-covered roads: pressure 70.3 and a 90% snow day chance. Set “Rarely closes” and the same storm gives 68%.
• Freezing rain. See the ice day calculator: 4 mm of freezing rain overnight with icy roads gives a 42% ice-day chance on its own.

How much snow for a snow day?

It depends far more on where you live than on any number. Districts in places that rarely see snow have fewer plows and less practice, and may close for an inch or two. Districts in the snow belt clear roads overnight and often open with several inches on the ground. That is why the calculator asks how easily your school closes instead of pretending one threshold fits everyone.

Timing matters as much as amount. Snow that stops at midnight gives crews hours to clear roads; the same snow falling at 6 a.m. lands on the morning commute. Snow during school hours counts at 50% because it leads to early dismissals rather than morning closures, and snow at a commute temperature above freezing is counted at a reduced share — down to 50% at +5 °C — because some of it melts on the roads.

The visual intensity of the animation (light below about 2 cm, moderate to 10 cm, heavy beyond) is only for the picture — it is not a closure rule.

Ice, freezing rain and rain

Freezing rain coats roads, sidewalks and bus steps in a glaze that salt and plows handle poorly, so a small amount can close schools that would stay open in several inches of snow. Enter it as freezing rain / ice accretion and it is scored as its own factor.

Ordinary rain is never turned into ice automatically. It counts as ice only when you choose a freezing condition — “Freezing rain”, “Ice”, “Snow + ice”, “Rain + freezing temperature” (all of it), or “Sleet / mixed” (half of it) — or when when at least 1 mm of rain (not already counted as ice) is followed by an overnight low of −1 °C or colder, 25% of that rain (at most 2 mm) is counted as possible ice. If you enter rain with a temperature at or below 0 °C under plain “Rain”, the page points out that you may want a freezing condition, and leaves the choice to you.

Cold, wind and wind chill

Some closures have no snow at all. When the wind chill is low enough, frostbite becomes a risk for children waiting at bus stops. A wind chill of −20 °C (−4 °F) or milder adds nothing, −28 °C (−18 °F) adds 10, −35 °C (−31 °F) adds 30, −40 °C (−40 °F) adds 45, −45 °C (−49 °F) adds 60, −55 °C (−67 °F) adds 75 points. The wind chill uses the formula the National Weather Service and Environment Canada share; type your own figure instead if your forecast gives one. For a closer look — your district’s own cold rule and time at the bus stop — use the cold day calculator. To work out wind chill on its own, use the wind chill calculator.

Wind also matters on its own when snow or ice is falling: sustained wind and gusts mean blowing and drifting snow and poor visibility. They count inside the “extras”, which are capped at 30 points so that wind can make a storm worse but cannot create a snow day by itself.

Today, tomorrow or any day

Because you enter the forecast, the calculator works for any day you have a forecast for — this morning, tomorrow, Friday or Monday. For tomorrow, take the snow expected from the evening before until the end of the school day, and the temperature and wind for bus time. For this morning, set the storm timing to the commute if it is still snowing, and describe the roads as they are.

Forecasts change, especially snowfall totals in the last 24 hours. Check your local forecast again the evening before and early in the morning, and enter the new figures.

School type, area and sensitivity

• How easily does your school close? — the biggest lever. A district that closes for an inch and one that opens through six are both normal somewhere.
• Area — long rural bus routes on untreated back roads close sooner than city schools where most students walk.
• Commute sensitivity — hills, back roads and long routes make bad roads matter more.
• School type — a private day school often follows the local district but may stay open more often; a boarding school’s students already live on campus.

These are your judgement about your area, not an official policy. Elementary, middle and high schools are not separate settings: a district almost always closes all of its schools together, because the buses are shared.

School vs college

Colleges and universities decide differently. Their students are adults, many live on campus, and classes can move online. The college snow day calculator needs noticeably more weather pressure before it gives a high closure chance, lets you describe your campus, and re-weights the storm timing for morning, afternoon or evening classes.

Who decides if school is closed?

In the US it is the school district — usually the superintendent, often after staff have driven bus routes before dawn and talked with road crews and neighbouring districts. The National Weather Service provides forecasts and warnings but does not close schools.

This page has no connection to any closure announcement, so it never says a school is closed. The calculator provides an estimate based on the conditions you enter; it is not a guarantee of a school closure. Most districts announce by early morning through their website, app, text alerts, social media and local TV and radio.

Snow days by state

The weather model is the same everywhere, but some states change what a closure means. Choose your state under “Location context” and the result shows the note too. The state is context only — it does not fetch anything.

As described when last checked in October 2026. Boards, districts and state rules can change from one winter to the next — always follow your own school’s announcement.

Michigan

Michigan law lets a district count up to six days of cancelled instruction for conditions outside its control (such as severe storms) as “forgiven”, and up to three more through a waiver; days beyond that have to be made up. Lake-effect snow falls in narrow bands, so neighbouring districts can decide differently.

New York City

Since 2020, New York City public schools have usually moved classes online when buildings close for a storm instead of taking a traditional snow day, although a traditional snow day has been allowed by state waiver (for example in February 2026). The approach can change from year to year, so check each announcement.

Pennsylvania

Districts with an approved Flexible Instructional Day program can turn up to five weather days a year into instruction at home, so a “closure” may be an FID rather than a day off. The state still recommends keeping make-up days in the calendar.

Minnesota

A district or charter school with an adopted plan may hold up to five e-learning days a year for inclement weather; they count as instruction days.

US and Canada

Choosing a country sets the units — °F, inches and mph for the United States; °C, centimetres and km/h for Canada — and the wording about who decides. Switching units converts the boxes; the result stays the same. Canada has its own page: the snow day calculator for Canada treats bus cancellations as a separate outcome, because in much of Ontario buses are cancelled while schools stay open, and it has the rules for Toronto, Ottawa, Barrie, Hamilton, Waterloo, Sudbury, Halifax, PEI and more.

How accurate is a snow day calculator?

Honestly: nobody knows a single number, and you should be wary of any site that quotes one without saying how it was measured. To claim an accuracy figure you would need a record of estimates made before each storm, the real decisions of the districts involved, and a count of hits and misses. That study has not been done for this model, so this page does not claim an accuracy percentage. It is a transparent estimate.

• The forecast you enter can change. Totals often shift in the last 24 hours, and a storm arriving two hours early or late changes everything.
• Borderline storms are hard. Two inches with temperatures near freezing can go either way; twelve inches rarely can.
• Districts differ. The settings let you describe yours, but they are your judgement.
• Things the weather cannot show: a district that has used up its snow days, a road-crew shortage, a power cut, or a decision made the night before.

Snow day rituals and superstitions

Every winter, students across the US and Canada try to “summon” a snow day. None of these rituals can change the weather — they are folklore, handed down by word of mouth, with no known single origin. They are also a fun family tradition on a stormy evening:

• Pajamas inside out (and sometimes backwards) — the best-known one.
• A spoon under the pillow — or on the windowsill, or in the freezer first.
• Flushing ice cubes down the toilet, one for each inch of snow wanted.
• A white crayon in the freezer, then under the pillow.
• A snow dance before bed, often around the kitchen table.

Two sensible rules: do not put anything down the toilet except a few ice cubes, and do not skip the homework because of a ritual.

Limitations

The estimate is only as good as the figures you enter, and the model is a set of heuristic assumptions, not a statistical fit to closure records. It does not know your district’s history, remaining snow days, staffing or road treatment, and it cannot see ice on the ground — only the amounts you type. Storm timing places the storm on a simple timeline; it is not an hourly forecast.

Frequently asked questions