How Snow Day Alerts Works

What Snow Day Alerts is designed to do

Snow Day Alerts estimates the likelihood of a school closure based on weather conditions that historically create difficult or unsafe travel during school mornings. The system is designed around one key reality: most closure decisions are made in a narrow early-morning window, usually between 4 and 5 AM.

Instead of looking only at daily snowfall totals, Snow Day Alerts focuses on timing, accumulation, and impact — the factors that matter most when districts decide whether buses can run safely.

Weather data inputs

For each ZIP code, the system analyzes short-range weather forecasts using:

• Overnight snowfall accumulation
• Snowfall and precipitation during the early-morning commute window
• Overnight precipitation combined with freezing hours as a risk proxy; actual ice and precipitation type are not identified
• Peak overnight/morning gusts; road-level drifting is not separately modeled
• Minimum temperatures during the overnight and morning windows; the current score does not separately calculate wind chill

Why timing matters more than totals

A storm that drops several inches during the afternoon may have little impact on schools the next day if roads are cleared overnight. On the other hand, even a modest amount of snow or ice that falls between midnight and sunrise can create dangerous conditions.

Snow Day Alerts places extra weight on weather conditions occurring from 6 PM through noon the following day, with the highest emphasis on the overnight and early-morning hours.

Regional adjustments

Snow readiness varies widely across the United States. Northern regions often remain open during moderate snowfall, while areas that see snow less frequently may close with much smaller amounts.

To reflect this reality, the scoring system adjusts expectations based on a predefined southern-state grouping, with different snow thresholds for other states. It does not learn individual district policies.

Scoring and interpretation

Current point rules, not measured closure rates

The southern group is TX, OK, AR, LA, MS, AL, TN, KY, GA, SC, NC, VA and FL. Its snow base is 35 points at 0.5 inches, 55 at 1, 70 at 2 and 85 at 3. Other states use 14 points at 0.5 inches, 24 at 1.5, 35 at 3, 48 at 5, 60 at 7 and 75 at 10. Only the highest matching base applies.

• Overnight snow adds 10 points at 1 inch or 15 at 2; morning snow adds 10 at 1 or 18 at 2.
• Overnight precipitation of at least 0.15 inches with at least three freezing hours adds 18 points (24 in the southern group). Otherwise at least 0.10 inches with at least one freezing hour adds 8 (12 in the southern group). This proxy does not diagnose freezing rain.
• Previous calendar-day snow adds 5 points at 2 inches or 10 at 4. Minimum window temperature adds 4 at 20°F or colder, or 8 at 10°F or colder.
• Peak window gusts add 3 points at 30 mph, 7 at 40, or 12 at 50. Only the highest matching tier in each factor applies.
• Less than 1 inch of window snow and less than 0.10 inches overnight precipitation caps the score at 35. Less than 2 inches and less than 0.25 inches caps it at 60. The final score is rounded and bounded to 0–100.

All weather factors are combined into a score from 0 to 100. The score is then translated into descriptive categories designed to be informative without overstating certainty:

• No Snow Day Signal (0–19%) – Little disruption signal.
• Tiny Snow Day Signal (20–39%) – A small signal to monitor.
• Low Snow Day Signal (40–54%) – Conditions may affect plans.
• Snow Day Possible (55–69%) – Watch for updates.
• Snow Day Watch (70–84%) – A stronger disruption signal.
• Snow Day Alert (85–100%) – The highest planning-signal category.

The displayed percentage is a rules-based planning score, not a statistically calibrated probability for a particular district. Commercial relationships never change the scoring rules or results.

Important limitations

Open “Why this score?” on a card for the actual cached weather inputs, regional rule group, applicable score ceilings, and weather-fetch time. The explanation replays the unchanged calculation and is withheld if it cannot match the result. Overnight means previous-day 6 PM to before 6 AM; morning means 6 AM to before noon, in the forecast location’s time zone. The first day may have only a partial overnight window.

Rules add points for window snow, overnight/morning thresholds, precipitation with freezing hours, previous-day snow, minimum temperature and peak gusts. Low snow/precipitation combinations can cap the score at 35 or 60. The final value is rounded and bounded to 0–100. Displayed new snow can be capped by the daily total while scoring uses the full window total. Missing inputs may produce defaults; stale weather can be reused after service errors. Neither establishes safe roads.

The output skips weekends but does not know district holidays or boundaries. See the Planning Center. No verified district accuracy study is published.

Snow Day Alerts does not use official school district data and does not predict individual district decisions. Local factors such as staffing, bus routes, road treatment priorities, and district policies can override weather conditions.

The odds are intended as a planning tool — not a guarantee. Always rely on your school district’s official communications for final decisions.