# Weather API Brief: Open-Meteo vs. US NWS API

Sources: official documentation only (fetched 2026-09-20).

## Comparison

| Factor | Open-Meteo | US NWS API |
|---|---|---|
| **Geographic coverage** | **Worldwide** — combines global models (GFS, ICON, ECMWF, etc.) and auto-selects the best for "any given location worldwide." [docs](https://open-meteo.com/en/docs) | **US only** (incl. territories/Alaska via WFO grids). A US-government service, not global. [docs](https://www.weather.gov/documentation/services-web-api) |
| **API key required?** | **No key** for the free tier. `apikey` is "Only required to commercial use" with a `customer-` prefix. [docs](https://open-meteo.com/en/docs) | **No key**, but a `User-Agent` identifying your app is **required** ("will be replaced with an API key in the future"). [docs](https://www.weather.gov/documentation/services-web-api) |
| **Attribution / identification** | Free use accepts the **CC-BY 4.0 licence** — attribution is required by that licence. [terms](https://open-meteo.com/en/terms) | **No attribution stated**; data is "intended to be open data, free to use for any purpose." A `User-Agent` with contact info is recommended so NWS can reach you. [docs](https://www.weather.gov/documentation/services-web-api) |
| **One limitation to plan around** | Free non-commercial tier caps at **<10,000 calls/day, 5,000/hour, 600/minute**; 15-min data is native only in Central Europe & North America. [terms](https://open-meteo.com/en/terms) | **US-only coverage** — unusable for any non-US location. Also the rate limit is **not public**, and cached gridX/gridY/office can change. [docs](https://www.weather.gov/documentation/services-web-api) |

## Recommendation (worldwide widget)

Use **Open-Meteo**. It is the only one of the two with worldwide coverage, needs no API key for non-commercial use, and documents explicit rate limits so you can plan. Budget for the free-tier caps (e.g., cache results), and honor the CC-BY 4.0 attribution requirement in your widget's footer.

NWS is excellent but **US-only**, so it cannot serve a worldwide widget on its own.

## Notes / non-claims
- No uptime guarantee is stated by either provider; Open-Meteo's terms explicitly disclaim warranties. [terms](https://open-meteo.com/en/terms)
- Open-Meteo's free tier is **non-commercial only**; commercial use requires a paid plan. The NWS docs state US-government open data "free to use for any purpose," but verify before any commercial deployment. [terms](https://open-meteo.com/en/terms) · [docs](https://www.weather.gov/documentation/services-web-api)
- API roots: Open-Meteo `https://api.open-meteo.com/v1/forecast`; NWS `https://api.weather.gov/` ([root](https://api.weather.gov/)).