Air quality index for Chiang Mai, as of (Asia/Bangkok). Values update hourly — see this page for the current reading and hourly forecast. Today's peak: AQI 89 at 18:00 local time.

airindex·today

Air Quality in Chiang Mai

Air quality in Chiang Mai is AQI 77 (moderate) right now, down from today's high of AQI 89 in the same band around 18:00. Today's main contributor is ozone, at 45 µg/m³. Today's hourly values spread widely, from AQI 49 up to AQI 89. The air is at its best today between 00:00 and 16:00, down to AQI 49.

Now, Oct 17at 19:00
77Moderate
Good0–50
Moderate51–100
Sensitive groups101–150
Unhealthy151–200
Very unhealthy201–300
Hazardous301+

By pollutant

  • O₃ ozone · sets the index nowAQI 77
  • PM₂.₅ fine particlesAQI 56
  • NO₂ nitrogen dioxideAQI 21
  • PM₁₀ coarse particlesAQI 14
  • SO₂ sulfur dioxideAQI 6
  • 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 Chiang Mai · Local time (GMT+7)

Today, Oct 17
Tomorrow, Oct 18
50
100
150
Peak 89 · 18:00
Peak 128 · 18:00
0:00
6:00
12:00
18:00
0:00
6:00
12:00
18:00

Good ≤ 50 · Moderate ≤ 100 · Sensitive groups ≤ 150

Now
Show hourly data table
TimeAQIPM₂.₅µg/m³PM₁₀µg/m³O₃µg/m³NO₂µg/m³SO₂µg/m³COmg/m³°C
Today
00:0054131327286.30.6727°
01:0053111128246.00.6126°
02:0052111125225.70.5726°
03:0051111121225.50.5525°
04:0051131317225.60.5725°
05:0050141510246.10.6625°
06:004918183.0276.90.7924°
07:0049191924246.20.8225°
08:0050232354196.10.7027°
09:0051181996115.90.5228°
10:005214141274.85.50.3929°
11:005311121362.54.70.3230°
12:005311121352.03.80.2931°
13:005411111332.03.20.2832°
14:005411111360.73.10.2632°
15:005411121390.03.40.2532°
16:007012121323.24.30.3031°
17:00861313107146.10.4630°
18:0089151573308.50.6829°
19:007721224542110.8828°
20:005823242949121.0127°
21:005625251853131.1227°
22:005626261156141.1927°
23:005727276.056141.2326°
Tomorrow
00:005828284.053141.2326°
01:006028284.051141.2226°
02:006127277.047121.1826°
03:0063252513439.11.1325°
04:0064232417397.11.1025°
05:0065222213376.11.1425°
06:006521217.0355.81.2125°
07:0066232316315.81.1925°
08:0066242455236.50.9927°
09:00662222108137.60.7029°
10:006617171485.78.40.4730°
11:006714141602.78.20.3831°
12:006713131572.17.60.3532°
13:006712131542.07.50.3333°
14:006713131571.28.40.3033°
15:007013141590.89.70.2833°
16:0010013141552.4110.2933°
17:0012114151397.4120.3632°
18:00128161611614140.4530°
19:0012119199721150.5430°
20:0010822228726160.6230°
21:009324248230180.7030°
22:007824257933190.7529°
23:006724257733190.7626°

Today at a glance

Cleanest air
00:00–16:00
around AQI 49
Worst hour
18:00
peaks at AQI 89
Tomorrow
Climbs past 100, peak 128
peak at 18:00

The week, hour by hour

Tomorrow crosses above 100, peaking at AQI 128 (unhealthy for sensitive groups) around 18:00. Over the 5-day forecast the daily peaks run Saturday (moderate), Sunday (unhealthy for sensitive groups), Monday (unhealthy for sensitive groups), Tuesday (unhealthy for sensitive groups), and Wednesday (unhealthy for sensitive groups), with Wednesday the worst of the stretch.

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 89 at 18:00
Thunderstorm32° / 24°
SunOct 18
Peak 128 at 18:00
Overcast33° / 25°
MonOct 19
Peak 119 at 18:00
Partly cloudy34° / 24°
TueOct 20
Peak 132 at 18:00
Partly cloudy34° / 25°
WedOct 21
Peak 140 at 18:00
Partly cloudy34° / 24°

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+
O₃ozone · sets the index now
77
PM₂.₅fine particles
56
NO₂nitrogen dioxide
21
PM₁₀coarse particles
14
SO₂sulfur dioxide
6
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: Insein · Lashio · Meiktila · Hinthada · Yangon

About Chiang Mai

CountryThailand, Chiang Mai
TimezoneAsia/Bangkok (UTC+7)
Coordinates18.79° N, 98.98° E
Population≈ 127K

Air quality in Chiang Mai — common questions

What is the air quality in Chiang Mai right now?

The current air quality index (AQI) in Chiang Mai is 77 (Moderate). Today's forecast peak is AQI 89 (Moderate) at 18:00 local time, and tomorrow's forecast peak is AQI 128. These values come from the CAMS forecast model, not from a local monitoring station.

When is air quality expected to be worst in Chiang Mai today?

Today's forecast puts the highest AQI in Chiang Mai at 18:00 in the evening, reaching 89. The largest contributor right now is O₃. 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 Chiang Mai tomorrow?

Tomorrow's forecast peak for Chiang Mai is AQI 128 (Unhealthy for Sensitive Groups) around 18:00 local time, higher than today's peak of 89. 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 Chiang Mai today?

The air quality index in Chiang Mai is set by O₃ right now. The modelled level this hour is 45 µg/m³, within the World Health Organization's 2021 guideline of 100 µg/m³. The others follow: PM₂.₅ (AQI 56), NO₂ (AQI 21), PM₁₀ (AQI 14), SO₂ (AQI 6), and CO (AQI 3).
Pollutant levels in Chiang Mai at the current hour
PollutantSub-indexLevelWHO 2021Vs guideline
O₃7745 µg/m³100 µg/m³ (8h)0.5×
PM₂.₅5621 µg/m³15 µg/m³ (24h)1.4×
NO₂2142 µg/m³25 µg/m³ (24h)1.7×
PM₁₀1422 µg/m³45 µg/m³ (24h)0.5×
SO₂611 µg/m³40 µg/m³ (24h)0.3×
CO30.88 mg/m³4 mg/m³ (24h)0.2×
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 Chiang Mai this week?

Over the 5-day forecast, daily peak AQI in Chiang Mai rises from 89 to 140. These are peak values: each day still has cleaner and dirtier hours, which the chart above shows.

How is air quality forecast for Chiang Mai, Chiang Mai, Thailand?

Air quality for Chiang Mai 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. Chiang Mai lies at 18.8° 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.