Weather APIs

Global air quality data — PM2.5, PM10, ozone, NO2, SO2, and AQI forecasts

NOAA NCEI historical climate data — global surface temps, precipitation, extremes

German Weather Service (DWD) open data — forecasts, radar, historical station data

River flood forecasts using GloFAS — discharge and return period data

Marine and ocean weather — wave height, swell, period, and sea surface temperature

Official US National Weather Service forecasts, alerts, and station observations

Historical weather data from 1940 to present — temperature, rain, wind at hourly resolution

Global weather forecasts — temperature, precipitation, wind, UV, and hourly/daily data

Free, open-source weather API. No signup required. Provides hourly and daily forecasts worldwide.