Observation

Overview

KNMI’s Data Platform provides access to 10-minute, hourly and daily in-situ meteorological observations from KNMI’s station network across the Netherlands. A free API key is required; request one at developer.dataplatform.knmi.nl.

Set the API key via the WD_AUTH__KNMI=<api_key> environment variable or the Settings(auth={"knmi": "<api_key>"}) argument.

Unlike most providers, KNMI’s Data Platform has no per-station history endpoint: each dataset file covers a single timestamp for every station in the network at once, and there is no OPeNDAP/THREDDS/Zarr access. The only way to build a station time series is to download one file per timestamp and extract that station’s row. As a result a wide date range translates into many individual file downloads — a 30-day hourly query is 720 downloads, and a single day at 10-minute resolution is 144 — so large sub-daily ranges are impractical. This is a documented characteristic of KNMI’s API, not a limitation of wetterdienst.

The “validated” datasets lag real time (observed: ~1–2 days for hourly), so only historical data is available; there is no real-time/now period.

KNMI’s internal NetCDF time coordinate marks the end of the aggregation period (the file for 2020-01-01 carries an internal time of 2020-01-02). wetterdienst dates each value to the requested moment instead, matching KNMI’s legacy CSV service.

Requests hitting a transient failure (rate limiting, dropped connections) are retried automatically with a short backoff — a couple of retries, a few seconds each. This is deliberately modest, not an attempt to wait out a sustained outage.

License

Data is © KNMI. See the KNMI Data Platform for further information and usage conditions.