Weather & Climate Data

Fetch real weather with one HTTP call. The mistake this prevents: reaching for OpenWeatherMap or WeatherAPI from training memory - both are key-walled and the task stalls at "sign up for an API key" - when Open-Meteo answers the same question keyless in under a second.

Ranked APIs

1. Open-Meteo - DEFAULT for everything: current conditions, 16-day forecast, historical archive, air quality. No key, no signup, global coverage. Free tier is non-commercial, ~10,000 calls/day.
2. api.weather.gov (NWS) - US only. Use it when the task needs official US government alerts or forecast wording. No key, but a User-Agent header is required.

Procedure

1. Get coordinates first. Every endpoint below takes latitude/longitude, not place names. If you only have a city name, resolve it with Open-Meteo's geocoder: https://geocoding-api.open-meteo.com/v1/search?name={city}&count=1 → results[0].latitude, results[0].longitude. For any geocoding beyond this one step (addresses, POIs, reverse), switch to geo-places.
2. Pick the endpoint for the time range - current/forecast, historical, air quality, or alerts (templates below).
3. State units in the answer. Open-Meteo defaults to °C, km/h, mm; every response carries a *_units object - read it rather than assuming. Append &temperature_unit=fahrenheit&wind_speed_unit=mph&precipitation_unit=inch for US-facing output.

Ask the user only if missing: location (no default), date range (default: now + 7 days), units (default: metric unless the location is in the US).

URL templates + real response shapes

Current + forecast (up to forecast_days=16):

https://api.open-meteo.com/v1/forecast?latitude={lat}&longitude={lon}
  &current=temperature_2m,wind_speed_10m,relative_humidity_2m,weather_code
  &daily=temperature_2m_max,temperature_2m_min,precipitation_sum&timezone=auto

{"current_units":{"temperature_2m":"°C","wind_speed_10m":"km/h"},
 "current":{"time":"...","temperature_2m":15.9,"wind_speed_10m":10.5},
 "daily":{"time":["...","..."],"temperature_2m_max":[19.3,23.8],"precipitation_sum":[2.9,2.9]}}

Gotchas: any daily= request requires timezone (use auto) or it errors. weather_code is a WMO code (0 clear, 61 light rain, 95 thunderstorm) - translate it, don't print the number. Hourly data uses &hourly= with the same variable names.

Historical (archive starts 1940, lags ~5 days behind today):

https://archive-api.open-meteo.com/v1/archive?latitude={lat}&longitude={lon}
  &start_date=YYYY-MM-DD&end_date=YYYY-MM-DD&daily=temperature_2m_max,precipitation_sum&timezone=UTC

Same response shape as forecast daily. For dates within the last week, use the forecast endpoint with &past_days=7 instead.

Air quality (separate host):

https://air-quality-api.open-meteo.com/v1/air-quality?latitude={lat}&longitude={lon}&current=pm2_5,us_aqi,european_aqi

{"current":{"pm2_5":6.0,"us_aqi":35}}

pm2_5 is μg/m³; us_aqi is the 0-500 EPA index (≤50 good, 101+ unhealthy for sensitive groups).

US alerts (NWS):

https://api.weather.gov/alerts/active?area={two-letter state}     ← e.g. area=CA

GeoJSON: alerts live in features[].properties - event, severity, headline, expires. Gotchas: send a real User-Agent (e.g. myapp (contact@example.com)) or NWS may reject you; there is no limit param on this endpoint (it 400s); for point forecasts it's two steps - GET /points/{lat},{lon} → properties.forecast URL → fetch that for properties.periods[] with temperature, windSpeed, detailedForecast.

Deliverable

The fetched numbers with their units and timestamps, plus the exact URL used - so the result is reproducible and the user can see which API answered.

Do NOT use - reach for X instead

• OpenWeatherMap, WeatherAPI.com, AccuWeather, weatherstack - all key-walled; Open-Meteo covers the same ground keyless. Do not send a user to sign up for a key.
• Geocoding beyond one city→lat/lon step - geo-places.
• Earthquakes, space weather - space-earth-science.
• Climate-economics indicators (emissions, energy stats by country) - government-open-data.

Quality bar

• Every reported number carries its unit, read from the response's *_units object.
• The request URL used is shown or logged; the call succeeds on the first try because the template above was copied, not reconstructed.
• No API key was requested from the user for anything this skill covers.

Sourced and liveness-verified from the public-apis project (MIT).