This page lists exactly where the numbers on this site come from. We do not use paid or private weather data.
Data sources used
- Values you enter. Most calculators (the main snow day calculator, wind chill, heat index, roof snow load, road salt, pipe freeze, snow removal and others) use only the numbers you type in. Nothing is fetched automatically.
- US National Weather Service API (api.weather.gov) — current forecast period (temperature, wind, short forecast, and quantitative snowfall where available) on US city predictor pages.
- Zippopotam.us — converts a US ZIP code into latitude/longitude so the NWS forecast can be requested.
- Open-Meteo (open-meteo.com) — forecast temperature, wind and snowfall on Canadian city predictor pages, plus geocoding of Canadian postal codes (by forward sortation area).
- Formulas: wind chill uses the 2001 JAG/TI formula adopted by the NWS and Environment and Climate Change Canada; heat index uses the NWS Rothfusz regression with the NWS low-temperature equation and adjustments.
Using official forecast data improves consistency, but it does not eliminate uncertainty. Weather forecasting is inherently probabilistic, and real-world outcomes can differ from modeled projections due to rapidly changing atmospheric conditions, localized effects, reporting delays, and forecast model limitations.
Calculator outputs and probability estimates are generated by applying transparent rule-based or statistical logic to incoming data signals. These outputs are automated interpretations, not official determinations.
Institutional decisions such as school closures, delays, or safety advisories are made using additional operational factors that are not available through public data feeds, including transportation readiness, staffing levels, infrastructure conditions, and local policy thresholds.
Important limitations to understand:
- Forecast inputs may be revised by the original data provider after publication
- API feeds can experience delays, outages, or regional gaps
- Local microclimate effects may not be fully captured in regional forecasts
- Institutional closure decisions include non-weather factors
- Probability scores are estimates, not guarantees
Whenever accuracy is critical, users should confirm conditions and decisions through official weather services, local authorities, and school district communications.
Found a result that looks wrong? Email adiwasikesha@gmail.com with the page and the values you entered.
References are for source transparency only and do not imply endorsement.
Methodology and data usage practices are periodically reviewed and refined to improve clarity and performance.