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

> Tomorrow.io Weather API scores 51.4 (D) on agent readiness against NOAA National Weather Service API (api.weather.gov)'s 49.6 (D), and leads in 4 of 7 scored categories. NOAA National Weather Service API (api.weather.gov) leads on security & auth and payments & pricing. Both do…

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- 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: 2026-10-08

Tomorrow.io Weather API scores 51.4 (D) on agent readiness against NOAA National Weather Service API (api.weather.gov)'s 49.6 (D), and leads in 4 of 7 scored categories. NOAA National Weather Service API (api.weather.gov) leads on security & auth and payments & pricing. Both do weather current.

- NOAA National Weather Service API (api.weather.gov): grade D, 49.6/100, rank #605 of 722. Markdown https://www.anchorterminal.com/tools/nws-api.md · JSON https://www.anchorterminal.com/api/v1/tools/nws-api.json
- Tomorrow.io Weather API: grade D, 51.4/100, rank #578 of 722. Markdown https://www.anchorterminal.com/tools/tomorrow-io.md · JSON https://www.anchorterminal.com/api/v1/tools/tomorrow-io.json

## 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:
- Security & auth, 53 against 34
- Payments & pricing, 60 against 20

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

Watch for: US and territories only

### Tomorrow.io Weather API (D)

Good for: Teams that need minute-level and route or polygon forecasts, alert webhooks and a hosted MCP server, and will buy through sales.

Ahead on:
- Reliability, 55 against 25
- Schema & documentation, 75 against 67
- Agent ergonomics, 73 against 66
- Maintenance & community, 27 against 8

Watch for: No public price for paid use. The plan table lists Free and Enterprise, the second by quote


## Score by category

| Category | Weight | NOAA National Weather Service API (api.weather.gov) | Tomorrow.io Weather API | Edge |
| --- | --- | --- | --- | --- |
| Reliability | 16% (20 this run) | 25 | 55 | Tomorrow.io Weather API +30 |
| Performance | 10%, pending | pending | pending | not scored in this run |
| Schema & documentation | 13% (16.2 this run) | 67 | 75 | Tomorrow.io Weather API +8 |
| Agent ergonomics | 13% (16.2 this run) | 66 | 73 | Tomorrow.io Weather API +7 |
| Security & auth | 14% (17.5 this run) | 53 | 34 | NOAA National Weather Service API (api.weather.gov) +19 |
| Payments & pricing | 10% (12.5 this run) | 60 | 20 | NOAA National Weather Service API (api.weather.gov) +40 |
| Task success | 10%, pending | pending | pending | not scored in this run |
| Maintenance & community | 7% (8.8 this run) | 8 | 27 | Tomorrow.io Weather API +19 |
| Transparency & trust | 7% (8.8 this run) | 63 | 63 | even |
| Negative events | ≤15 | 0 | 0 | |
| **Total** | | **49.6 · D** | **51.4 · D** | |

## Facts side by side

| Fact | NOAA National Weather Service API (api.weather.gov) | Tomorrow.io Weather API |
| --- | --- | --- |
| Kind | HTTP API | HTTP API |
| Vendor | National Weather Service | The Tomorrow Companies Inc. |
| Hosted endpoint | `https://api.weather.gov` | `https://api.tomorrow.io/v4` |
| Transports | HTTP | HTTP |
| Auth | None | OAuth or key |
| Pricing | Free | Freemium |
| x402 | no | no |
| Licence | Public domain (data) | Proprietary service under Tomorrow.io's subscription terms |
| Tools exposed | none | 11 |
| Read-only variant documented | no | no |
| llms.txt | no | yes |
| Last release | 2026-03-19 | 2026-07-14 |
| Terms last updated | no date given | couldn't be read |
| Privacy policy last updated | no date given | couldn't be read |
| Customer content may train models | not found in the text | couldn't be read |
| Terms restrict automated access | not found in the text | couldn't be read |
| Terms restrict benchmarking | not found in the text | couldn't be read |
| Terms or service can change without notice | not found in the text | couldn't be read |
| Arbitration or class-action waiver | not found in the text | couldn't be read |
| 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.

**Tomorrow.io Weather API.** A public OpenAPI 3.1 file, Markdown docs with llms.txt and a hosted MCP server with 11 tools suit agents, and a free plan exists. Paid prices are by quote only, free keys are barred from commercial use, the docs give no numeric rate limits, and the status page lists 50 incidents in 85 days, mostly stale or degraded data.

## 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

### Tomorrow.io Weather API

1. Send the key in the `apikey` header, not the query string, so it stays out of URLs and logs
2. Request only the `fields` and `timesteps` needed on POST /timelines. Free plans cover 24 hours back and 5 days ahead at `1h` and `1d`
3. Split archive requests. POST /historical takes at most 31 days per call and deducts tokens, 1 for a point and 10 for a polygon
4. Treat 401 with code 401001 as a missing or bad key. The docs say 403, the live API answered 401 on 8 October 2026
5. On 429 back off without a hint. `Retry-After` is documented only for 503
6. Check the plan's terms before storing or reselling responses. Free accounts are limited to non-commercial use with a Powered by Tomorrow.io link

## Questions

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

Tomorrow.io Weather API scores 51.4 (D) on agent readiness against NOAA National Weather Service API (api.weather.gov)'s 49.6 (D), and leads in 4 of 7 scored categories. NOAA National Weather Service API (api.weather.gov) leads on security & auth and payments & pricing.

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

NOAA National Weather Service API (api.weather.gov) needs no key. Tomorrow.io Weather API takes an API key or an OAuth sign-in.

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

Yes. NOAA National Weather Service API (api.weather.gov) has a hosted endpoint at https://api.weather.gov and Tomorrow.io Weather API at https://api.tomorrow.io/v4.


## For agents

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

## Other comparisons with NOAA National Weather Service API (api.weather.gov) or Tomorrow.io Weather API

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- [NOAA National Weather Service API (api.weather.gov) vs The Weather Company Data APIs](https://www.anchorterminal.com/compare/nws-api-vs-weather-company.md)
- [NOAA National Weather Service API (api.weather.gov) vs WeatherAPI.com](https://www.anchorterminal.com/compare/nws-api-vs-weatherapi-com.md)
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- [NOAA National Weather Service API (api.weather.gov) vs Xweather Weather API](https://www.anchorterminal.com/compare/nws-api-vs-xweather.md)
- [OpenWeather One Call API vs Tomorrow.io Weather API](https://www.anchorterminal.com/compare/openweather-one-call-vs-tomorrow-io.md)
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