French weather forecasts and alerts.
Météo-France API is a free Weather API that requires apiKey authentication, is served over HTTPS and has unconfirmed CORS support.
Details from portail-api.meteofrance.fr.

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Multi-model weather: GFS, ECMWF AIFS/IFS and a 31-member GEFS ensemble, keyless point forecasts
The Météo-France API is provided by MeteofranceWeb (portail-api.meteofrance.fr).
Yes. The Météo-France 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 Météo-France API uses apiKey authentication, so you need to register for credentials before making requests.
CORS support for the Météo-France API is unknown. Test a request from the browser, and fall back to a server-side call if it is blocked.
Yes. The Météo-France API is served over HTTPS, so it's safe to use in production.