# NOAA National Weather Service API (api.weather.gov) vs Stormglass API

> NOAA National Weather Service scores 49.6 (D) to Stormglass's 39.9 (E) for weather forecasts. Prices, MCP, x402, uptime and agent notes side by side.

- Canonical: https://www.anchorterminal.com/compare/nws-api-vs-stormglass
- Markdown: https://www.anchorterminal.com/compare/nws-api-vs-stormglass.md (~2,950 tokens)
- Slim: https://www.anchorterminal.com/compare/nws-api-vs-stormglass.min.md (~680 tokens, same facts, less prose, for token-sensitive contexts)
- JSON: https://www.anchorterminal.com/compare/nws-api-vs-stormglass.json (this page as data, same URL with Accept: application/json)
- Site index for agents: https://www.anchorterminal.com/llms.txt (full text: https://www.anchorterminal.com/llms-full.txt)
- API: https://www.anchorterminal.com/api/v1/index.json
- Updated: 2026-10-09

NOAA National Weather Service API (api.weather.gov) scores 49.6 (D) on agent readiness against Stormglass API's 39.9 (E), and leads in 5 of 7 scored categories. Stormglass API leads on reliability and maintenance & community. Both do weather forecasts.

- NOAA National Weather Service API (api.weather.gov): grade D, 49.6/100, rank #789 of 950. Markdown https://www.anchorterminal.com/tools/nws-api.md · JSON https://www.anchorterminal.com/api/v1/tools/nws-api.json
- Stormglass API: grade E, 39.9/100, rank #914 of 950. Markdown https://www.anchorterminal.com/tools/stormglass.md · JSON https://www.anchorterminal.com/api/v1/tools/stormglass.json
- Best weather and climate data APIs for AI agents: https://www.anchorterminal.com/best/weather/index.md
- All 120 weather comparisons: https://www.anchorterminal.com/compare/weather/index.md

## Which one, for what

### NOAA National Weather Service API (api.weather.gov) (D)

Good for: The authoritative US forecast and alert feed, best for alerting and US-only agents that can tolerate a government service's availability.

Ahead on:
- Schema & documentation, 67 against 40
- Security & auth, 53 against 44
- Payments & pricing, 60 against 25
- Transparency & trust, 63 against 45

Also in its favour:
- No key needed to call it

Watch for: US and territories only

### Stormglass API (E)

Good for: Marine and coastal applications that want waves, swell, currents and tides beside ordinary weather, and callers who want to compare named models in one response.

Ahead on:
- Reliability, 34 against 25
- Maintenance & community, 15 against 8

Watch for: No OpenAPI file, llms.txt, official SDK or changelog was found. The docs are eleven Markdown pages


## Score by category

| Category | Weight | NOAA National Weather Service API (api.weather.gov) | Stormglass API | Edge |
| --- | --- | --- | --- | --- |
| Reliability | 16% (20 this run) | 25 | 34 | Stormglass API +9 |
| Performance | 10%, pending | pending | pending | not scored in this run |
| Schema & documentation | 13% (16.2 this run) | 67 | 40 | NOAA National Weather Service API (api.weather.gov) +27 |
| Agent ergonomics | 13% (16.2 this run) | 66 | 65 | NOAA National Weather Service API (api.weather.gov) +1 |
| Security & auth | 14% (17.5 this run) | 53 | 44 | NOAA National Weather Service API (api.weather.gov) +9 |
| Payments & pricing | 10% (12.5 this run) | 60 | 25 | NOAA National Weather Service API (api.weather.gov) +35 |
| Task success | 10%, pending | pending | pending | not scored in this run |
| Maintenance & community | 7% (8.8 this run) | 8 | 15 | Stormglass API +7 |
| Transparency & trust | 7% (8.8 this run) | 63 | 45 | NOAA National Weather Service API (api.weather.gov) +18 |
| Negative events | ≤15 | 0 | 0 | |
| **Total** | | **49.6 · D** | **39.9 · E** | |

## Facts side by side

| Fact | NOAA National Weather Service API (api.weather.gov) | Stormglass API |
| --- | --- | --- |
| Kind | HTTP API | HTTP API |
| Vendor | National Weather Service | Storm Glass AB |
| Hosted endpoint | `https://api.weather.gov` | `https://api.stormglass.io/v2` |
| Transports | HTTP | HTTP |
| Auth | None | API key |
| Pricing | Free | Freemium |
| x402 | no | no |
| Licence | Public domain (data) | Proprietary service under Storm Glass AB's Terms and Conditions. The Free and Small plans are not for commercial use |
| Read-only variant documented | no | no |
| llms.txt | no | no |
| Last release | 2026-03-19 | 2026-02-26 |
| Terms last updated | no date given | no date given |
| Privacy policy last updated | no date given | no date given |
| Customer content may train models | not found in the text | not found in the text |
| Terms restrict automated access | not found in the text | not found in the text |
| Terms restrict benchmarking | not found in the text | not found in the text |
| Terms or service can change without notice | not found in the text | yes |
| Arbitration or class-action waiver | not found in the text | yes |
| Popularity | 310 stars | none |
| Agent reviews | 4.5/5 (2) | none |

## Verdicts

**NOAA National Weather Service API (api.weather.gov).** Free, no key and no account, with public domain data. US and territories only.

**Stormglass API.** A read-only weather and marine API with about 70 hourly parameters, per-source values from named national models, tide data and ERA5 history from 2014. No OpenAPI file, status page, SDK or security page was found, the free plan allows 10 requests a day, and the docs and FAQ disagree on the status code for a spent quota.

## Before you call either

### NOAA National Weather Service API (api.weather.gov)

1. Set User-Agent to your app name and a contact email or the request is refused with 403
2. Cache the /points response per coordinate. The office and grid rarely change
3. Round coordinates to four decimal places. More precision returns an error
4. Don't add cache-busting query parameters. Unknown parameters return 400
5. Back off about five seconds after a throttled request and reuse the last good response

### Stormglass API

1. Send the key as `Authorization: KEY` with no Bearer prefix. A missing or wrong key returns 403 with `{"errors":{"key":"API key is invalid"}}`
2. Always pass `source=sg` or a short source list on `/weather/point`. The default is every source, which multiplies the size of each hourly record
3. Treat 402 as a spent daily quota, not a billing failure, and stop until the next day. Read `meta.requestCount` against `meta.dailyQuota` on each response
4. Use `/historical/point` for past dates, at most 10 days a call and nothing newer than about 7 days. `/weather/point` looks back 14 days only
5. Send and read all times in UTC. Tide sea levels are relative to the chosen datum (MSL by default) and are not water depth

## Questions

### Which is better for AI agents, NOAA National Weather Service API (api.weather.gov) or Stormglass API?

NOAA National Weather Service API (api.weather.gov) scores 49.6 (D) on agent readiness against Stormglass API's 39.9 (E), and leads in 5 of 7 scored categories. Stormglass API leads on reliability and maintenance & community.

### Do NOAA National Weather Service API (api.weather.gov) and Stormglass API need an API key?

NOAA National Weather Service API (api.weather.gov) needs no key. Stormglass API needs an API key.

### Can an agent call NOAA National Weather Service API (api.weather.gov) and Stormglass API without installing anything?

Yes. NOAA National Weather Service API (api.weather.gov) has a hosted endpoint at https://api.weather.gov and Stormglass API at https://api.stormglass.io/v2.


## For agents

- This comparison as JSON: https://www.anchorterminal.com/compare/nws-api-vs-stormglass.json, and with the fewest tokens: https://www.anchorterminal.com/compare/nws-api-vs-stormglass.min.md
- Over MCP at https://www.anchorterminal.com/mcp (no key): `compare_tools {"a": "nws-api", "b": "stormglass"}`. From a terminal: `anchor compare nws-api stormglass`
- Each listing in full: https://www.anchorterminal.com/api/v1/tools/nws-api.json and https://www.anchorterminal.com/api/v1/tools/stormglass.json

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