HUMIDITY TRACKER
How Humid Is Hong Kong Right Now? Live Data + the 回南天 Season
Quick answer
The live humidity tile below comes directly from the Hong Kong Observatory's open data for its "Hong Kong Observatory" station, updated every few minutes. The seasonal chart underneath is built from HKO's historical climatological daily-mean relative-humidity data, which lags live conditions by roughly six weeks — it's a historical trend view, not a live figure. We keep these two layers clearly labelled and separate, and never merge them into anything resembling an "official index." Everything below the chart marked as interpretation is Averta's own reading, not an HKO position.
Live humidity
Monthly humidity trend (by year)
This page's data is pulled directly from Hong Kong Observatory public data; it is not an HKO official page. Live humidity shows its own fetch time above; the monthly chart's latest complete data is as of May 2026 (page checked: 2026-07-13).
HKO data
Hong Kong's Observatory explains that "回南天" happens when the winter monsoon weakens and warm, moist southerly marine air meets surfaces — walls, floors — that haven't warmed up yet, causing condensation to form directly on them, typically during the winter-to-spring transition.
Why does 回南天 make everything so damp? (Averta's interpretation)
The following is Averta's own interpretation, not an HKO statement:
during a 回南天 episode, indoor humidity can rise noticeably over a short period, and combined with condensation on surfaces, this creates favourable conditions for mould growth (EPD's guidance recommends keeping indoor humidity below 70% — see our Mould Removal & Prevention service). The damp risk window extends well beyond 回南天 itself, through a longer wet season.
What to do when humidity is high
- Dehumidify and ventilate — bathrooms, kitchens and wardrobes need particular attention; run the extractor fan after a shower, leave a gap for airflow in closed wardrobes.
- Watch for standing water or damp spots — under air-conditioner drip trays, around windows, on ceilings; dry these promptly — EPD recommends drying within 24-48 hours to reduce mould risk.
- Already seeing mould? Check whether that spot has been persistently humid before assuming the worst; if mould has already appeared, we can run a moisture source check: Mould Removal & Prevention service.
- Mould dispute with a landlord or tenant? Responsibility depends on whether it's ordinary wear and tear, tenant negligence, or a structural leak — see Who's Responsible for Mould in a Hong Kong Rental?.
Home feeling damp and worried about mould? WhatsApp us a photo and we'll help you find the source first
Frequently asked questions
How often is this humidity data updated?
The live tile follows HKO's "Hong Kong Observatory" station open data, updated every few minutes. The monthly seasonal chart uses the historical climatological CSV, which we re-fetch monthly and which lags roughly six weeks behind live conditions — so treat that layer as a historical trend, not a live figure.
Is this an official HKO "mould risk index"?
No. HKO does not publish a mould risk index, and we haven't invented one to look official either. This page clearly separates "HKO data" (live humidity, historical humidity trend) from "Averta's interpretation" (our own read on 回南天/mould risk) — the two should never be conflated.
What humidity level counts as "dangerous"?
HKO doesn't publish a fixed "dangerous humidity" figure, and we're not going to invent one either. EPD's guidance is to keep indoor relative humidity below 70% to help prevent mould — that's a reference benchmark for prevention, not a safe/dangerous health index.