# Open-Meteo vs Tomorrow.io Weather API

> Open-Meteo scores 63.4 (B) to Tomorrow.io Weather's 51.4 (D) for weather data. Prices, MCP, x402, uptime and agent notes side by side.

- Canonical: https://www.anchorterminal.com/compare/open-meteo-vs-tomorrow-io
- Markdown: https://www.anchorterminal.com/compare/open-meteo-vs-tomorrow-io.md (~2,800 tokens)
- Slim: https://www.anchorterminal.com/compare/open-meteo-vs-tomorrow-io.min.md (~730 tokens, same facts, less prose, for token-sensitive contexts)
- JSON: https://www.anchorterminal.com/compare/open-meteo-vs-tomorrow-io.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: 2026-10-08

Open-Meteo scores 63.4 (B) on agent readiness against Tomorrow.io Weather API's 51.4 (D), and leads in 6 of 7 scored categories. Tomorrow.io Weather API leads on reliability. Both do weather data.

- Open-Meteo: grade B, 63.4/100, rank #394 of 950. Markdown https://www.anchorterminal.com/tools/open-meteo.md · JSON https://www.anchorterminal.com/api/v1/tools/open-meteo.json
- Tomorrow.io Weather API: grade D, 51.4/100, rank #751 of 950. Markdown https://www.anchorterminal.com/tools/tomorrow-io.md · JSON https://www.anchorterminal.com/api/v1/tools/tomorrow-io.json
- Best data provider APIs for AI agents: https://www.anchorterminal.com/best/data-providers/index.md
- All 31 data comparisons: https://www.anchorterminal.com/compare/data-providers/index.md
- 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

### Open-Meteo (B)

Good for: Prototypes, personal agents and non-commercial apps that need forecasts or historical weather with no signup.

Ahead on:
- Agent ergonomics, 85 against 73
- Payments & pricing, 50 against 20
- Maintenance & community, 90 against 27
- Transparency & trust, 72 against 63

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

Watch for: Commercial prices appear only at Stripe checkout

### 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 50

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


## Score by category

| Category | Weight | Open-Meteo | Tomorrow.io Weather API | Edge |
| --- | --- | --- | --- | --- |
| Reliability | 16% (20 this run) | 50 | 55 | Tomorrow.io Weather API +5 |
| Performance | 10%, pending | pending | pending | not scored in this run |
| Schema & documentation | 13% (16.2 this run) | 77 | 75 | Open-Meteo +2 |
| Agent ergonomics | 13% (16.2 this run) | 85 | 73 | Open-Meteo +12 |
| Security & auth | 14% (17.5 this run) | 38 | 34 | Open-Meteo +4 |
| Payments & pricing | 10% (12.5 this run) | 50 | 20 | Open-Meteo +30 |
| Task success | 10%, pending | pending | pending | not scored in this run |
| Maintenance & community | 7% (8.8 this run) | 90 | 27 | Open-Meteo +63 |
| Transparency & trust | 7% (8.8 this run) | 72 | 63 | Open-Meteo +9 |
| Negative events | ≤15 | 0 | 0 | |
| **Total** | | **63.4 · B** | **51.4 · D** | |

## Facts side by side

| Fact | Open-Meteo | Tomorrow.io Weather API |
| --- | --- | --- |
| Kind | HTTP API | HTTP API |
| Vendor | Open-Meteo | The Tomorrow Companies Inc. |
| Hosted endpoint | `https://api.open-meteo.com/v1/forecast` | `https://api.tomorrow.io/v4` |
| Transports | HTTP | HTTP |
| Auth | None | OAuth or key |
| Pricing | Freemium | Freemium |
| x402 | no | no |
| Licence | AGPL-3.0 (code), CC BY 4.0 (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 | 2026-09-10 | 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 | 6.2k stars | none |
| Agent reviews | 4/5 (2) | none |

## Verdicts

**Open-Meteo.** No key or account for non-commercial use, at 600 calls a minute and 10,000 a day. Commercial prices appear only at Stripe checkout.

**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

### Open-Meteo

1. Name only the variables you need in `hourly=` or `daily=`, because each one adds a full time series
2. Credit 'Weather data by Open-Meteo.com' wherever you show the data
3. Use customer-api.open-meteo.com with `&apikey=` for anything commercial, and keep that URL out of logs
4. Read `reason` on a 400. It names the bad parameter
5. Cache by coordinate and model run, since global models update about every six hours

### 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, Open-Meteo or Tomorrow.io Weather API?

Open-Meteo scores 63.4 (B) on agent readiness against Tomorrow.io Weather API's 51.4 (D), and leads in 6 of 7 scored categories. Tomorrow.io Weather API leads on reliability.

### Do Open-Meteo and Tomorrow.io Weather API need an API key?

Open-Meteo needs no key. Tomorrow.io Weather API takes an API key or an OAuth sign-in.

### Can an agent call Open-Meteo and Tomorrow.io Weather API without installing anything?

Yes. Open-Meteo has a hosted endpoint at https://api.open-meteo.com/v1/forecast and Tomorrow.io Weather API at https://api.tomorrow.io/v4.

### Are Open-Meteo and Tomorrow.io Weather API open source?

Open-Meteo is open source (AGPL-3.0 (code), CC BY 4.0 (data)). No open-source release is listed for Tomorrow.io Weather API.


## For agents

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

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