Open Meteo

When to use

• You need weather forecasts (hourly/daily/current) for coordinates.
• You need air quality / pollen forecasts (hourly/current) for coordinates.
• You need to resolve a user-provided place name to coordinates and timezone (geocoding).
• You need to support multi-location batching (comma-separated lat/lon lists).
• You need a deterministic checklist for Open-Meteo query parameters, response parsing, and error handling.

Goal

Provide a reliable, production-friendly way to call Open-Meteo APIs (Forecast, Air Quality, Geocoding), choose variables, control time/units/timezone, and parse responses consistently.

Steps

1. Pick the correct API and base URL

   • Forecast: https://api.open-meteo.com/v1/forecast
   • Air Quality: https://air-quality-api.open-meteo.com/v1/air-quality
   • Geocoding: https://geocoding-api.open-meteo.com/v1/search

2. Resolve coordinates (if you only have a name)

   • Call Geocoding with name and optional language, countryCode, count.
   • Use the returned latitude, longitude, and timezone for subsequent calls.

3. Design your time axis (timezone, timeformat, and range)

   • Prefer timezone=auto when results must align to local midnight.
   • If you request daily=..., set timezone (docs: daily requires timezone).
   • Choose timeformat=iso8601 for readability, or timeformat=unixtime for compactness.
     • If using unixtime, remember timestamps are GMT+0 and you must apply utc_offset_seconds for correct local dates.
   • Choose range controls:
     • forecast_days and optional past_days, or
     • explicit start_date/end_date (YYYY-MM-DD), and for sub-daily start_hour/end_hour.

4. Choose variables minimally (avoid "download everything")

   • Forecast: request only the variables you need via hourly=..., daily=..., current=....
   • Air Quality: request only the variables you need via hourly=..., current=....
   • Keep variable names exact; typos return a JSON error with error: true.

5. Choose units and model selection deliberately

   • Forecast units:
     • temperature_unit (celsius / fahrenheit)
     • wind_speed_unit (kmh / ms / mph / kn)
     • precipitation_unit (mm / inch)
   • Forecast model selection:
     • default models=auto / “Best match” combines the best models.
     • you can explicitly request models via models=....
     • provider-specific forecast endpoints also exist (provider implied by path). See references/models.md (section "Endpoints vs models=") for examples and doc links.
     • for provider/model-specific selection tradeoffs, see references/models.md.
   • Air Quality domain selection:
     • domains=auto (default) or cams_europe / cams_global.

6. Implement robust request/response handling

   • Treat HTTP errors and JSON-level errors separately.
   • JSON error format is:
     • {"error": true, "reason": "..."}
   • When requesting multiple locations (comma-separated coordinates), expect the JSON output shape to change to a list of structures.
   • Optionally use format=csv or format=xlsx when you need data export.

7. Validate correctness with a “known city” check

   • Geocode “Berlin” → Forecast hourly=temperature_2m for 1–2 days → verify timezone and array lengths.
   • Air Quality hourly=pm10,pm2_5,european_aqi → verify units and presence of hourly_units.

Critical prohibitions

• Do not include out-of-scope APIs in this skill’s implementation guidance: Historical Weather, Ensemble Models, Seasonal Forecast, Climate Change, Marine, Satellite Radiation, Elevation, Flood.
• Do not omit timezone when requesting daily variables (per docs).
• Do not assume unixtime timestamps are local time; they are GMT+0 and require utc_offset_seconds adjustment.
• Do not silently ignore {"error": true} responses; fail fast with the provided reason.
• Do not request huge variable sets by default; keep queries minimal to reduce payload and avoid accidental overuse.

Definition of done

• You can geocode a place name and obtain coordinates/timezone.
• You can fetch Forecast data with at least one hourly, one daily (with timezone), and one current variable.
• You can fetch Air Quality data for at least one pollutant and one AQI metric.
• Your client code handles both HTTP-level failures and JSON-level error: true with clear messages.
• Attribution requirements from the docs are captured for Air Quality (CAMS) and Geocoding (GeoNames).

Links

• Official docs (in-scope):
  • https://open-meteo.com/en/docs
  • https://open-meteo.com/en/docs/air-quality-api
  • https://open-meteo.com/en/docs/geocoding-api
• Skill references:
  • references/forecast-api.md
  • references/models.md
  • references/weather-codes.md
  • references/air-quality-api.md
  • references/geocoding-api.md
  • references/examples.md