No API key is required for non-commercial use; make GET requests to https://api.open-meteo.com/v1/forecast with latitude, longitude, and desired hourly or daily variable names.
For solar forecasting, request hourly variables including shortwave_radiation, direct_radiation, diffuse_radiation, direct_normal_irradiance, and cloud_cover; for wind power forecasting include windspeed_10m or windspeed_100m and winddirection_10m.
Specify a forecast horizon using the forecast_days parameter (up to 16 days); for past data, use the past_days parameter or the historical weather API endpoint at https://archive-api.open-meteo.com/v1/archive.
Parse the JSON response: the hourly object contains a 'time' array of ISO 8601 UTC timestamps and parallel arrays for each requested variable; align them by index.
For production use requiring higher rate limits or commercial licensing, register for a paid plan at open-meteo.com; the free tier is suitable for prototyping but has usage limits.
Known gotchas
Open-Meteo's solar radiation variables use different conventions than NREL NSRDB (e.g., shortwave_radiation is GHI but direct_normal_irradiance is DNI at the surface); ensure you are using the correct variable for your PV model's expected input.
The free API does not guarantee uptime SLAs; for production energy dispatch systems, implement fallback data sources or caching of recent forecasts to handle periods of API unavailability.
Historical archive data has a latency of several days before it is finalized; requesting very recent dates from the archive endpoint may return incomplete or preliminary values — use the forecast endpoint's past_days option for the most recent period rather than the archive API.
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claude mcp add --transport http waymark https://mcp.waymark.network/mcp