The calculator starts with the weather expected for your selected date, then asks whether the timing and local setting resemble conditions that commonly put school transportation under pressure.
Step 1: Find the forecast location
A city or postal-code search is resolved through Open-Meteo's geocoding service. The browser then requests a seven-day forecast for those coordinates. We do not require an account, and the web app does not send the search to our own server. Read the details in the privacy policy.
Step 2: Read weather variables
The live request includes daily snowfall, rain, total precipitation, precipitation probability, minimum and maximum temperature, and maximum wind. Hourly snowfall is used to estimate the evening-to-morning window. The source definitions are documented by Open-Meteo's forecast API.
The result also groups hourly snowfall into four visible periods: the previous evening, overnight, the 5–9 a.m. bus window and school hours. Switching between U.S. and metric display units converts what you see, while the underlying score remains unchanged.
Official U.S. alerts are checked separately
For supported U.S. coordinates, the browser also checks the National Weather Service API for active winter weather alerts. Relevant warnings, watches and advisories appear beside the result with a link to the official local forecast. The alert check is non-blocking, so a temporary NWS outage does not prevent the forecast estimate from loading.
Official alerts are safety context, not another hidden score input. They do not increase or decrease the six-factor percentage because the current model has not been calibrated against a verified district-decision dataset. Read our guide to winter weather alerts before interpreting a watch or warning as a school decision.
Step 3: Score six factors
| Factor | Weight | What it represents |
|---|---|---|
| Snow and ice | 35% | Daily and overnight snow plus a cautious near-freezing rain signal |
| Temperature | 18% | Average cold, persistence below freezing and refreeze pressure |
| Wind chill | 12% | Bus-stop exposure, blowing snow and extreme-cold pressure |
| Morning timing | 15% | Snowfall from the prior evening through roughly 8 a.m. |
| Area and routes | 12% | Broad urban, suburban or rural transportation context |
| School level | 8% | A general sensitivity adjustment by selected school level |
Local settings only add pressure when winter hazards or extreme cold are present. Choosing “Rural” cannot turn a clear, mild forecast into a high result. The district tendency setting makes a small adjustment to a non-zero estimate; it does not override the weather.
Every published threshold
The weights above are only half of the method. Below is the full set of thresholds each factor uses, transcribed from the calculator's source code rather than paraphrased for readability. If one of these numbers changes in the code and not on this page, the build fails, which is deliberate.
Two of the rules refer to winter precipitation being present. That condition is met when the forecast shows at least 0.25 in (0.6 cm) of snow for the day or overnight, or when the minimum temperature is at or below freezing alongside at least 0.02 in of total precipitation.
Snow and ice 35%
The larger of the day's forecast snowfall total and the overnight figure.
- 8 in (20 cm) or more scores 100
- 5 in (13 cm) or more scores 88
- 3 in (7.6 cm) or more scores 72
- 1.5 in (3.8 cm) or more scores 55
- 0.5 in (1.3 cm) or more scores 32
- Anything below that scores 0
Icing override: when the minimum temperature is at or below 32°F, the maximum is at or below 37°F, some rain is forecast and precipitation probability is at least 35%, the score is raised to at least 82 if forecast rain reaches 0.1 in, otherwise to at least 58.
Temperature 18%
The average of the forecast minimum and maximum.
- 5°F or below scores 100
- 15°F or below scores 82 with winter precipitation, 55 without
- 24°F or below scores 65 with winter precipitation, 25 without
- 31°F or below scores 45 with winter precipitation, 8 without
- 34°F or below scores 22, but only with winter precipitation
- Otherwise 0
Wind chill 12%
The standard wind chill formula applied to the average temperature and the day's maximum wind. Above 50°F, or below 3 mph of wind, it returns the plain temperature.
- −15°F or below scores 100
- −5°F or below scores 82
- 5°F or below scores 68 with winter precipitation, 40 without
- 15°F or below scores 42 with winter precipitation, 15 without
- Otherwise 45 if wind reaches 35 mph alongside winter precipitation, else 0
Morning timing 15%
Hourly forecast snowfall from 6 p.m. the previous evening through 8 a.m..
- 4 in (10 cm) or more scores 100
- 2 in (5 cm) or more scores 78
- 1 in (2.5 cm) or more scores 55
- 0.5 in (1.3 cm) or more scores 35
- Otherwise 0
Area and routes 12%
The area type you select.
- Rural scores 68
- Suburban scores 50
- Urban scores 38
Reset to 0 whenever there is no winter precipitation and wind chill is above −5°F, so a mild forecast cannot be pushed upward by this setting.
School level 8%
The school level you select.
- Elementary scores 65
- Middle scores 55
- High scores 45
- College scores 25
Reset to 0 under the same mild-forecast condition as the area factor.
What happens after the six scores
- Each factor score is multiplied by its weight and the six results are summed.
- District tendency adjusts that sum by +9 for “usually closes earlier” or −9 for “usually stays open longer”, and only when the sum is already above 5.
- If there is no winter precipitation and wind chill is above 5°F, the result is capped at 8. A calm, mild day cannot produce a high number no matter which settings are chosen.
- The value is rounded and clamped to the 0–100 range, then given a band label.
No hidden inputs. There is no random component, no undisclosed adjustment and no scraped district data. Everything that moves the number is either a forecast variable listed above or a setting you chose yourself. Read who builds and maintains this for how that is kept true.
Step 4: Translate the score into a planning label
- 0–25: Low — limited closure pressure in the current forecast.
- 26–50: Watch — some relevant signals, but conditions remain borderline.
- 51–75: Elevated — meaningful disruption is possible; prepare a backup plan.
- 76–100: High — the weather strongly favors closure or a major schedule change.
These labels deliberately avoid “certain.” Our prediction accuracy guide explains why a transparent estimate is more useful than an unsupported guarantee.
What is outside the model
The estimate does not directly observe road treatment, bus staffing, building utilities or district leadership decisions. Read how schools make the actual call and the complete limitations statement before relying on a result.
Best use: check in the evening to prepare, refresh in the morning, and treat the district's message as final.
Applying the method to a specific place
The same six factors run everywhere, but which of them carries the result changes by location. In a lake-effect city the snow and morning-timing rows usually dominate; on the prairies it is far more often temperature and wind chill. Each city page names the factors that typically lead locally and explains why, and the prediction map scores every published city with identical settings so the comparison is like for like.
Before acting on any result, read the accuracy and limitations statement. It is the companion to this page: this one describes what the model does, that one describes what it cannot see.
Method last reviewed against the source code on .