Air quality index for Hong Kong, as of (Asia/Hong_Kong). Values update hourly — see this page for the current reading and hourly forecast. Today's peak: AQI 84 at 00:00 local time.

airindex·today

Air Quality in Hong Kong

Hong Kong is now at AQI 68 (moderate), below today's high of AQI 84 in the same band around 00:00. Today's main contributor is fine particulate matter (PM₂.₅), at 23 µg/m³. The WHO 24-hour guideline is 15 µg/m³, so today's level runs at about 1.5× that value.

Now, Oct 17at 20:00
68Moderate
Good0–50
Moderate51–100
Sensitive groups101–150
Unhealthy151–200
Very unhealthy201–300
Hazardous301+

By pollutant

  • PM₂.₅ fine particles · sets the index nowAQI 68
  • O₃ ozoneAQI 59
  • NO₂ nitrogen dioxideAQI 31
  • PM₁₀ coarse particlesAQI 23
  • SO₂ sulfur dioxideAQI 18
  • CO carbon monoxideAQI 3
Unusually sensitive people should consider reducing prolonged or intense outdoor activity

Modeled forecast data. AQI values come from atmospheric models (CAMS via Open-Meteo), not local monitoring stations. Readings can differ from ground-level conditions — for exact street-level values, consult an official air quality station near you. The forecast is calculated for a grid square, roughly 11 km across Europe and 45 km elsewhere, and air quality can vary within one square.

The next 48 hours

Hourly air quality index for Hong Kong · Local time (GMT+8)

Today, Oct 17
Tomorrow, Oct 18
50
Peak 84 · 00:00
Peak 65 · 00:00
0:00
6:00
12:00
18:00
0:00
6:00
12:00
18:00

Good ≤ 50

Now
Show hourly data table
TimeAQIPM₂.₅µg/m³PM₁₀µg/m³O₃µg/m³NO₂µg/m³SO₂µg/m³COmg/m³°C
Today
00:008430355570370.3626°
01:008427326655340.3226°
02:008424297543310.3026°
03:008422277836290.2826°
04:008420247933290.2726°
05:008318227832280.2726°
06:008318227337300.2926°
07:008221256645320.3226°
08:008111137743330.3227°
09:007911138737310.3127°
10:0077111410127290.2828°
11:0076121611321270.2728°
12:0075141912118260.2628°
13:0074162112618260.2628°
14:0073182312820260.2628°
15:0072182312424270.2728°
16:0072182311631280.2828°
17:0071192410738300.2928°
18:007021269647310.3127°
19:006922278557320.3327°
20:006823277663330.3427°
21:006822277360310.3426°
22:006720247251290.3226°
23:006618227344260.3026°
Tomorrow
00:006516207538250.2826°
01:006415187732240.2726°
02:006314177929230.2626°
03:006213177926230.2626°
04:006113167826230.2626°
05:006013167627240.2626°
06:006014177132260.2826°
07:005918216538280.2926°
08:005918216341290.3027°
09:006016206934290.2828°
10:006016207824280.2428°
11:006116218716270.2129°
12:006117229413270.2029°
13:006117229913260.2029°
14:0061172310114260.2129°
15:006117229917280.2129°
16:006117229321300.2129°
17:006118228528320.2329°
18:006120247541340.2728°
19:006125296356370.3227°
20:006127305267380.3527°
21:006129324571380.3627°
22:006231333971360.3526°
23:006331353371350.3526°

Today at a glance

Worst hour
00:00
peaks at AQI 84
Tomorrow
Better, peak 65
peak at 00:00

The week, hour by hour

The index backs off tomorrow, peaking at AQI 65 (moderate) around 00:00. The 5-day outlook reads Saturday (moderate), Sunday (moderate), Monday (unhealthy for sensitive groups), Tuesday (unhealthy for sensitive groups), and Wednesday (unhealthy) — Wednesday looks the worst.

Each cell is one forecast hour, coloured by air quality band. A ring marks the day's worst hour. The blue ring marks the current hour.

TodayOct 17
Peak 84 at 00:00
Overcast28° / 26°
SunOct 18
Peak 65 at 00:00
Partly cloudy29° / 26°
MonOct 19
Peak 117 at 23:00
Partly cloudy30° / 25°
TueOct 20
Peak 121 at 02:00
Partly cloudy30° / 26°
WedOct 21
Peak 157 at 18:00
Partly cloudy33° / 26°

Pollutants right now

Every pollutant on the same AQI scale as the big number above. The index only ever equals the worst score — pollutants don't add up.

050100150+
PM₂.₅fine particles · sets the index now
68
O₃ozone
59
NO₂nitrogen dioxide
31
PM₁₀coarse particles
23
SO₂sulfur dioxide
18
COcarbon monoxide
3
GoodModerateUnhealthy for Sensitive GroupsUnhealthyVery UnhealthyHazardous

The colors cover a wide area, not a street. The forecast works in squares of roughly 11 km across Europe and 45 km elsewhere, so the air where you actually are can differ from the shade under the city.

Check air quality in: Zhuhai · Guangzhou · Wong Tai Sin · Huizhou · Shenzhen

About Hong Kong

CountryHong Kong
TimezoneAsia/Hong Kong (UTC+8)
Coordinates22.28° N, 114.17° E
Population≈ 7.4M

Air quality in Hong Kong — common questions

What is the air quality in Hong Kong right now?

The current air quality index (AQI) in Hong Kong is 68 (Moderate). Today's forecast peak is AQI 84 (Moderate) at 00:00 local time, and tomorrow's forecast peak is AQI 65. These values come from the CAMS forecast model, not from a local monitoring station.

When is air quality expected to be worst in Hong Kong today?

Today's forecast puts the highest AQI in Hong Kong at 00:00 during the night, reaching 84. The largest contributor right now is PM₂.₅. Air quality shifts through the day with traffic, wind, how well the air mixes and sunlight, so the hourly chart above shows the pattern for today and tomorrow.

What will the air quality be in Hong Kong tomorrow?

Tomorrow's forecast peak for Hong Kong is AQI 65 (Moderate) around 00:00 local time, lower than today's peak of 84. A next-day forecast is less certain than today's, so check back in the morning for the updated hourly curve.

Which pollutants drive the AQI in Hong Kong today?

The air quality index in Hong Kong is set by PM₂.₅ right now. The modelled level this hour is 23 µg/m³ — 1.5× the World Health Organization's 2021 guideline of 15 µg/m³. The others follow: O₃ (AQI 59), NO₂ (AQI 31), PM₁₀ (AQI 23), SO₂ (AQI 18), and CO (AQI 3).
Pollutant levels in Hong Kong at the current hour
PollutantSub-indexLevelWHO 2021Vs guideline
PM₂.₅6823 µg/m³15 µg/m³ (24h)1.5×
O₃5976 µg/m³100 µg/m³ (8h)0.8×
NO₂3163 µg/m³25 µg/m³ (24h)2.5×
PM₁₀2327 µg/m³45 µg/m³ (24h)0.6×
SO₂1833 µg/m³40 µg/m³ (24h)0.8×
CO30.34 mg/m³4 mg/m³ (24h)0.1×
The overall AQI is the highest of the six sub-indices, so the pollutant with the highest sub-index is the one setting the number shown on this page. Sub-indices are computed over the EPA's averaging periods, while the levels are modelled values for the current hour.

Is air quality improving in Hong Kong this week?

Over the 5-day forecast, daily peak AQI in Hong Kong rises from 84 to 157. These are peak values: each day still has cleaner and dirtier hours, which the chart above shows.

How is air quality forecast for Hong Kong, Hong Kong?

Air quality for Hong Kong is forecast with the Copernicus Atmosphere Monitoring Service (CAMS), operated by ECMWF. CAMS models hourly levels of PM2.5, PM10, ozone, nitrogen dioxide, sulfur dioxide and carbon monoxide. Hong Kong lies at 22.3° N in the Northern Hemisphere, which sets the seasonal pattern of sunlight that drives much of the chemistry behind these pollutants. AQI values on this page use the US EPA scale.
About the Air Quality Index

What is the Air Quality Index (AQI)?

The Air Quality Index (AQI) is a tool developed by the U.S. Environmental Protection Agency (EPA) to communicate how clean or polluted the air is and what health effects may be of concern. The AQI runs from 0 to 500 and is divided into six color-coded categories: Good, Moderate, Unhealthy for Sensitive Groups, Unhealthy, Very Unhealthy, and Hazardous.

How do I read the AQI values?

Lower AQI values mean cleaner air. An AQI of 0–50 (green) is Good, 51–100 (yellow) is Moderate, 101–150 (orange) is Unhealthy for Sensitive Groups, 151–200 (red) is Unhealthy, 201–300 (purple) is Very Unhealthy, and 301–500 (maroon) is Hazardous. When the AQI exceeds 100, air quality is considered unhealthy — at first for sensitive groups, then for everyone as the AQI rises.

Who are the sensitive groups?

Sensitive groups include people with heart or lung disease, older adults, children and teenagers, people who are pregnant, and people who are active outdoors. These groups are more likely to be affected when air quality is poor. If you are in a sensitive group, you can reduce your exposure by taking fewer and shorter outdoor walks when the AQI is elevated.

Which pollutants are measured?

The AQI covers five major pollutants regulated under the Clean Air Act: ground-level ozone (O₃), particle pollution (PM₂.₅ and PM₁₀), carbon monoxide (CO), sulfur dioxide (SO₂), and nitrogen dioxide (NO₂). An AQI value is calculated for each pollutant, and the highest value determines the overall AQI.

Where does the air quality data come from?

The hourly air quality data comes from the Copernicus Atmosphere Monitoring Service (CAMS), which provides global atmospheric composition forecasts. The data is accessed via Open-Meteo, which provides free, open-source weather and air quality APIs. The AQI categories and health guidance follow the EPA AirNow technical standard (EPA-454/B-24-002).

What are the health effects of poor air quality?

Poor air quality can cause respiratory issues, aggravate asthma and allergies, and increase the risk of cardiovascular problems. Fine particles (PM₂.₅) can penetrate deep into the lungs and bloodstream. The World Health Organization estimates that air pollution causes millions of premature deaths worldwide each year.

How often is the air quality forecast updated?

The CAMS air quality forecast is updated regularly using atmospheric models. Weather data such as temperature and cloud cover comes from Open-Meteo. The forecast provides up to 5 days of hourly air quality predictions.

AQI Levels (US EPA Standard)

Good (0–50) — Air quality is satisfactory — it's a great day to be active outside
Moderate (51–100) — Unusually sensitive people should consider reducing prolonged or intense outdoor activity
Unhealthy for Sensitive Groups (101–150) — Sensitive groups should reduce prolonged or intense outdoor activity. Take more breaks and watch for symptoms such as coughing or shortness of breath
Unhealthy (151–200) — Everyone should reduce prolonged or intense outdoor activity. Sensitive groups should avoid outdoor exertion. Consider moving activities indoors
Very Unhealthy (201–300) — Everyone should avoid prolonged or intense outdoor exertion. Sensitive groups should avoid all outdoor physical activity. Move activities indoors or reschedule
Hazardous (301–500) — Health warning — everyone should avoid all outdoor physical activity. Stay indoors and keep activity levels light. Follow tips for keeping particle levels low indoors

AQI categories and health guidance: EPA AirNow (EPA-454/B-24-002, May 2024). Air quality data: CAMS/Copernicus via Open-Meteo.