Data sources

api.weather.gov powers weather forecasts, current conditions, watch/warning alerts, and the gridpoint precipitation series that drives the mud score. No API key; we send a descriptive User-Agent per NWS policy.

developer.nps.gov provides park alerts and closures for every NPS unit in our coverage (Shenandoah, C&O Canal, Rock Creek, Harpers Ferry, Catoctin, Great Falls VA, Prince William Forest, Assateague, and the Appalachian Trail).

airnowapi.org provides AQI and primary pollutant at coordinates. Used when AIRNOW_API_KEY is configured.

openstreetmap.org provides the base map layer on our trail map and supplies reference coordinates for some curated trails.

Sunrise, sunset, and daylight-remaining are computed locally from published astronomical formulas. No API dependency.

State park closure and alert feeds vary in quality. Best-effort scrapers; gracefully fall back to no-data when the agency page format changes.

Trail descriptions, distances, elevation gain, surface types, and amenities are hand-curated from publicly available park-service materials. Corrections and additions: hello@itsatrailday.com.