HUMIDITY TRACKER
How Humid Is Hong Kong Right Now? Live Data + the 回南天 Season
Quick answer
The live humidity tile below uses Hong Kong Observatory open data from the "Hong Kong Observatory" station and updates every few minutes. The seasonal chart uses HKO historical climatological daily-mean relative-humidity data for the past 12 months. It shows completed months only, so it is for reading a trend rather than live conditions. We label these two data layers separately and do not combine them into an "official index." Any interpretation below the chart is Averta's own, not an HKO position.
Based on Hong Kong Observatory public data compiled by Averta Pest Control (as of 2026-08), this page tracks Hong Kong's monthly mean relative humidity over the last 12 months for damp-season planning.
Live humidity
Monthly humidity trend (by year)
Scroll sideways to see all months ↔
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 Aug 2026 (page checked: 2026-09-15).
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. Combined with condensation on surfaces, this creates conditions more favourable to mould growth (EPD guidance recommends keeping indoor humidity below 70%; see our Mould Removal & Prevention service). The damp period often extends beyond 回南天 into 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? First check whether the spot has been persistently humid. If mould has appeared, we can carry out 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? Explore mould-removal options
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 shows completed months only — 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.