🌤️ Free Open-Source Weather API | Open-Meteo.com | WarmIndex

Open-Meteo is a free, open-source weather API providing high-resolution forecasts and 80+ years of historical data worldwide to developers and researchers without requiring an API key.

🚀 Overview

Open-Meteo is an open-source weather API that delivers accurate, high-resolution weather forecasts (1-11 km) and historical data by partnering with national weather services like NOAA, DWD, ECMWF, and others. It aggregates the best global and mesoscale models for reliable predictions updated hourly.

This project solves the problem of limited access to free, high-quality weather data APIs, which often require keys, payments, or have restrictions. It's built for developers integrating weather into apps, websites, and tools; researchers training ML models on vast historical datasets; and indie makers avoiding vendor lock-in.

We built it to democratize weather data, making open-source models from public services easily accessible via a simple JSON API, promoting fair use and self-hosting for scalability.

✨ Key Features

High-resolution forecasts (1-11 km) with up to 16-day hourly predictions and current weather, using real-time data from satellites, radar, and more
80+ years of historical hourly weather data at 10 km resolution, ideal for climate analysis and ML training
Simple, keyless JSON-over-HTTP API supporting parameters like latitude/longitude, variables (temperature, wind, precipitation), with client libraries in Python, JS, etc.
Open-source under AGPLv3, self-hostable for unlimited calls, plus specialized APIs like climate, elevation, and marine
Optional: Weather maps integration, expanding model coverage (e.g., AIFS from ECMWF)

🛠 Tech Stack

Frontend: Svelte, TypeScript (website and maps)
Backend: Rust, C (data processing and OM file format), Swift
Database: Custom OMfiles format for efficient storage/retrieval
Auth: None for free tier / API keys for commercial subscriptions
Hosting: Self-hosted or cloud (Vercel-like for website, custom servers for API)

👥 Who Is This For?

This project is useful for:

Developers who want to integrate free, accurate weather data into apps without API keys
Teams looking for global forecasts and historical data for analytics or simulations
Indie makers building weather apps, dashboards, or IoT projects
Researchers analyzing climate trends or training weather prediction models

📸 Screenshots / Demo

Live demo: https://open-meteo.com (API playground), https://maps.open-meteo.com/ (interactive maps)
GitHub: https://github.com/open-meteo

🔥 Project Status

🟢 Actively building

Last updated: 2026-03-24

❓ FAQ

Is this project free?

Freemium (Free for non-commercial use with fair usage up to 10,000 calls/day; commercial subscriptions from $29/month for 1M calls, higher tiers available).

Is the source code available?

Yes — https://github.com/open-meteo

Can I contribute?

Yes — report issues, submit pull requests on GitHub repositories, or provide feedback via tickets.open-meteo.com. Community contributions welcome for new models, libraries, or improvements.