IPMA
Portuguese weather and climate data
Dutch weather, radar and climate data.
KNMI API is a free Weather API that requires apiKey authentication, is served over HTTPS and has unconfirmed CORS support.
Details from developer.dataplatform.knmi.nl.

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The KNMI API is provided by KNMI Developer portal Home (developer.dataplatform.knmi.nl).
Yes. The KNMI API is listed in the Weather category of the public-apis directory, which only includes APIs that are free or have a free tier. Check its documentation for rate limits and paid plans.
Yes. The KNMI API uses apiKey authentication, so you need to register for credentials before making requests.
CORS support for the KNMI API is unknown. Test a request from the browser, and fall back to a server-side call if it is blocked.
Yes. The KNMI API is served over HTTPS, so it's safe to use in production.