Data sources
Every number on this site comes from public U.S. government data, processed by code you can read. Here's what we use, how, and under what terms.
| Source | What we use | How often | Terms |
|---|---|---|---|
| National Weather Service API | Gridpoint forecast (snowfall, ice, temperature, wind chill, precipitation chance, weather type) and active alerts for your forecast zone | Fetched when you look, then shared by everyone in the same grid cell for up to 15 minutes | NWS data is open; requests identify this site and a contact address, as NWS asks |
| NOAA NCEI U.S. Climate Normals 1991-2020 | Annual snowfall normal (ANN-SNOW-NORMAL) at the nearest station within 80 km; standard (30-year) and provisional (10+ year) normals | Downloaded once (version 1.0.1, accessed 2026-11-09) | Public domain U.S. government data |
| U.S. Census Bureau 2020 Gazetteer, ZCTA file | A central point for each of 33,144 ZIP Code Tabulation Areas | Downloaded once (accessed 2026-11-09) | Public domain U.S. government data |
NWS /points service | Which NWS grid cell, forecast zone and time zone each ZIP area's central point falls in | Mapped once in November 2026; re-checked monthly, since NWS occasionally changes grid assignments | As above |
What we don't use
No school-district closure feeds, no social media, and no paid weather data. We don't announce closures; your district does.
Where the ZIP code goes
Your ZIP code stays in your browser. To find your grid cell, the page loads a small file for the first three digits of the ZIP code (the same file for everyone in that range), then asks for the forecast for that grid cell. If you use "Use my location", your position is rounded to about 1 km before it's sent, and only to find the grid cell.
Model changelog
| Version | Date | What changed and why |
|---|---|---|
| v0.1 | 2026-11-10 | First version. Factors and starting weights chosen by hand as a starting point; not yet fitted to outcomes. |
The full method, with every weight, is on How it works.