National Weather Service API (api.weather.gov)

The National Weather Service public REST API delivers real-time weather forecasts, alerts, observations, gridded forecast data, aviation weather products, and metadata for offices, zones, and radar stations across the United States and US territories. Responses default to GeoJSON with content negotiation for JSON-LD, CAP, ATOM, and DWML. No API key is required — only a unique User-Agent string identifying the calling application. Stable production endpoint at api.weather.gov, current spec version 3.9.2.