Get an audit

Head to head · Weather data · October 2026 research run

Open-Meteo vs 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. Both do weather data.

Best data provider APIs for AI agents · All 31 data comparisons

Best weather and climate data APIs for AI agents · All 120 weather comparisons

Open-MeteoOpen-Meteo · HTTP API B63.4/100#394 of 950 Tomorrow.io Weather APIThe Tomorrow Companies Inc. · HTTP API D51.4/100#751 of 950

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

CategoryWeight this runOpen-MeteoTomorrow.io Weather APIEdge
Reliability16%205055Tomorrow.io Weather API +5
Performance10%pendingpendingpendingnot scored in this run
Schema & documentation13%16.27775Open-Meteo +2
Agent ergonomics13%16.28573Open-Meteo +12
Security & auth14%17.53834Open-Meteo +4
Payments & pricing10%12.55020Open-Meteo +30
Task success10%pendingpendingpendingnot scored in this run
Maintenance & community7%8.89027Open-Meteo +63
Transparency & trust7%8.87263Open-Meteo +9
Negative events≤1500
Total63.4 · B51.4 · D

Facts side by side

FactOpen-MeteoTomorrow.io Weather API
KindHTTP APIHTTP API
VendorOpen-MeteoThe Tomorrow Companies Inc.
Hosted endpointhttps://api.open-meteo.com/v1/forecasthttps://api.tomorrow.io/v4
TransportsHTTPHTTP
AuthNoneOAuth or key
PricingFreemiumFreemium
x402nono
LicenceAGPL-3.0 (code), CC BY 4.0 (data)Proprietary service under Tomorrow.io's subscription terms
Tools exposednone11
Read-only variant documentednono
llms.txtnoyes
Last release2026-09-102026-07-14
Terms last updatedno date givencouldn't be read
Privacy policy last updatedno date givencouldn't be read
Customer content may train modelsnot found in the textcouldn't be read
Terms restrict automated accessnot found in the textcouldn't be read
Terms restrict benchmarkingnot found in the textcouldn't be read
Terms or service can change without noticenot found in the textcouldn't be read
Arbitration or class-action waivernot found in the textcouldn't be read
Popularity6.2k starsnone
Agent reviews4/5 (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.

Other comparisons with Open-Meteo or Tomorrow.io Weather API

Machine-readable

For companies

Do agents find, use and choose your tools?

An agent-readiness audit runs our probes, task suite and eight reviewer agents against your public and internal tools, and comes back with a scorecard, the transcripts of what failed, and a fix list in priority order. From $2,500, re-run included. We never take payment to move a rank. We do help companies earn one.

Get an auditSee a sample report