OpenWeer

An open weather platform for the Netherlands, built on KNMI open data.

openweer.nl — animated rain radar, per-location 2-hour minute-by-minute rain forecast, current observations, and short-range hourly forecast extending to ~48 hours via HARMONIE-AROME.

Inspired by popular rain radar companies, OpenWeer is powered exclusively by the KNMI Open Data Platform (CC-BY-4.0).

Status

🚧 Pre-alpha. Building publicly, in steps. See CLAUDE.md for engineering rules.

Architecture (1 minute)

   KNMI MQTT  ──►  ingest worker  ──►  raw HDF5/GRIB on disk
                                              │
                                              ▼
                                       tiler worker
                                       (HDF5 → PNG XYZ tiles)
                                              │
                                              ▼
   browser  ◄──  nginx/Caddy  ◄──┬── /tiles/* (static PNG)
                                 ├── /api/*   (FastAPI)
                                 └── /        (React Router v7 SSR)

A single VPS, four Docker services, no database. See the implementation plan for milestones.

Tech stack

Layer	Choice
Backend	Python 3.13 · FastAPI · asyncio · httpx · aiomqtt · h5py · rasterio
Frontend	React Router v7 (framework mode) · MapLibre GL · Tailwind · TypeScript
Reverse proxy	Caddy (auto-TLS)
Deploy	Docker Compose on a single VPS (Hetzner / DigitalOcean)

Quickstart

git clone git@github.com:robertkeus/openweer.git
cd openweer
cp .env.example .env       # edit KNMI_API_KEY
docker compose up

Full local-dev instructions land with Step 6.

Development

The api/ and web/ packages can be developed independently.

# Backend
cd api
uv sync --all-extras
uv run pytest
uv run ruff check .

# Frontend (Step 5+)
cd web
npm ci
npm run dev

Attribution

Weather data © KNMI, CC-BY-4.0. See DATA_LICENSE.md.

OpenWeer source code is MIT-licensed. See LICENSE.