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Hong Kong Observatory vs RainViewer

Same instrument, two spec sheets — measured, not claimed.

APIHong Kong ObservatoryNEW—RainViewerNEW—
Uptime · 30d
Uptime · 90d—%—%
Uptime · 30d—%—%
P50 · ms——
P95 · ms——
Authnonenone
CORSyesyes
HTTPSyesyes
Card requirednono
Commercial useunclearunclear
Data licenseHKO open data (see terms of use)Unverified (attribution requested)
Free tierFree, no keyFree — limits not published
Rate limitUnpublishedUnpublished
In directory since2026-07-052026-07-05
operationalpartialdownno data

Hong Kong Observatory vs RainViewer: common questions

Which is more reliable, Hong Kong Observatory or RainViewer?

On our scheduled checks, RainViewer leads on measured uptime — Hong Kong Observatory at —% versus RainViewer at —% over 90 days. These are our own probe results, not provider claims; the uptime bars above show the day-by-day record for both.

Do Hong Kong Observatory and RainViewer need an API key?

Neither needs a paid key — Hong Kong Observatory is callable with no signup, and RainViewer is callable with no signup. Both are quick to prototype with; rate limits still apply.

Can I call Hong Kong Observatory and RainViewer from the browser?

Yes — both Hong Kong Observatory and RainViewer send CORS headers over HTTPS, so front-end code can fetch either directly with no backend proxy. That makes them easy to swap in a client-side app while you compare responses.

Are Hong Kong Observatory and RainViewer free for commercial use?

Hong Kong Observatory has unclear commercial terms, and RainViewer has unclear commercial terms. We track service terms and the data license as separate fields — see the Commercial use and Data license rows above, and confirm both before shipping either in a paid product.