Hong Kong Observatory vs openSenseMap

The Hong Kong Observatory's Open Data API exposes roughly 50 machine-readable datasets covering real-time weather observations, 9-day forecasts, lightning counts, tropical cyclone tracking, tidal predictions, UV index and radiation levels, plus historical rainfall and sunshine records, for Hong Kong and nearby waters. It is a free, keyless service built for machine-to-machine consumption, mirrored on the government's data.gov.hk portal alongside the Observatory's own documented endpoint.

openSenseMap is the open, non-profit citizen-science platform behind the University of Munster's senseBox project, serving live and historical readings from thousands of crowdsourced environmental sensor stations worldwide, covering not just temperature/humidity but also particulate matter, noise and other phenomena. Reading data is fully open and keyless (accounts are only needed to register or post data from your own senseBox), and the full historical archive is separately mirrored on an archive subdomain.