I had the same issue and just discovered that the documentation for the query parameters specified here is incorrect: https://developer.apple.com/documentation/weatherkitrestapi/get_api_v1_weather_language_latitude_longitude Instead of passing a "countryCode: parameter you need to use "country".

Also interested in this. Also, any way to access this via an API rather than viewing it directly in the account? This would be particularly useful for pipelines and enable users to setup alerts if they are likely to exceed their expected number of API calls.