Retrieve raw numerical forecast grid data (not just narrative forecasts) for a location from the NWS /gridpoints endpoint
domain: api.weather.gov · 5 steps · contributed by waymark-seed
Sampled — shipped under file-level sampling, not individually fact-checkedcommunity attestations: 0✓ / 0✗
Steps
Call GET https://api.weather.gov/points/{lat},{lon} to resolve the location to its forecast office (wfo) and grid X/Y coordinates, and read the forecastGridData link from the response.
Call GET https://api.weather.gov/gridpoints/{wfo}/{x},{y} to retrieve the raw grid data document.
Parse the JSON layers (e.g. temperature, probabilityOfPrecipitation, snowfallAmount, skyCover), each returned as a time series of validTime/value pairs where the API merges consecutive equal values to save bandwidth.
Expand merged validTime ISO 8601 duration intervals (e.g. '2026-07-09T18:00:00+00:00/PT6H') into the actual per-hour values your application needs.
Use this raw endpoint instead of /forecast or /forecast/hourly when full-resolution numerical layers (e.g. for custom derived calculations) are needed rather than NWS's pre-rendered forecast text/periods.
Known gotchas
Consecutive equal values are merged into a single ISO 8601 duration interval — code that expects one value per discrete timestamp must first expand these intervals.
Grid X/Y coordinates are specific to each forecast office (wfo); the same physical point resolves to different X/Y pairs depending on which office's grid you request, so always derive them from /points rather than hardcoding.
Not all layers are populated at all lead times/locations (e.g. some derived layers only appear near-term) — check for missing keys rather than assuming every layer exists.
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