Free Weather APIs

Forecast, historical, marine and air-quality data from national weather models

Catch: Commercial use needs a paid plan; attribution required (CC BY 4.0)

Global point forecasts from the Norwegian Meteorological Institute

Catch: Must send a unique User-Agent and cache responses or you get throttled

US forecasts, alerts and observations from the National Weather Service

Catch: US locations only; a User-Agent header is required

Current weather, forecasts and geocoding

Catch: Free plan covers only current weather and basic forecasts

Real-time, forecast, history, astronomy and search endpoints

Catch: Commercial use allowed; free plan limits history and forecast days

Historical and forecast weather in one timeline endpoint

Catch: Daily record cap; heavier use needs a paid plan

Hyperlocal forecasts, minute-level nowcasts and weather alerts

Catch: Free plan has lower rate limits and limited history

Dark Sky-compatible forecast API built on NOAA models

Catch: Donation raises the limit; signup required

Marine and surf weather: waves, tides, water temperature

Catch: Not for commercial use

Plain-text and JSON weather over curl, no signup

Catch: Community-run; no SLA and informal rate limits

JSON API for German Weather Service (DWD) forecasts and observations

Catch: Mostly Germany and nearby; community-hosted

Open air-quality measurements from stations worldwide

Catch: Needs a free key; rate limits apply

US air-quality index observations and forecasts from the EPA

Catch: US-focused; rate limits apply

METAR, TAF, PIREP and SIGMET data from NOAA

Catch: Rate limited; cache responses