Vietnam Charted

Air quality & climate · 9 cities

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Monthly air quality from IQAir’s 2025 city data beside long-term station climate normals for Sa Pa, Hà Nội, Hạ Long, Huế, Đà Nẵng, Nha Trang, Đà Lạt, Vũng Tàu and Hồ Chí Minh City. Pick a month, filter cities, and hover anything for the numbers and where they came from.

Chưa được dịch, nên đang hiển thị bằng tiếng Anh.

Month
Cities

October at a glance

Air quality for October 2025 and typical daily temperatures, humidity and rainfall, ranked from cleanest to dirtiest air.

Cleanest air[1]

≈25Good
via Phan Thiet

Dirtiest air[1]

92Moderate

Hottest afternoons[2]

32°C

Coolest nights[2]

14°C

Air quality map, October

Dot colour is the US AQI category; the number is the monthly AQI.

Sa Pano air dataHà NộiAQI 92Hạ LongAQI 69HuếAQI 29Đà NẵngAQI 51Nha TrangAQI ≈55Đà LạtAQI 41Vũng TàuAQI ≈25Hồ Chí Minh CityAQI 73
Good ≤50Moderate ≤100Unhealthy for sensitive groups ≤150Unhealthy ≤200No air data
Source: IQAir [1], AQI categories US EPA [5], outlines Natural Earth [8]links a city to the stand-in city whose monitors supply its air data

Ranked by air quality, October

Select a city for its full profile and sources.

Source: IQAir 2025 monthly data [1]; IBST station normals via Wikipedia [2][3]; HCMC rain WMO [4]≈ = nearby stand-in city · Unranked: Sa Pa (no monitor nearby)

Air-quality calendar

Every city with IQAir data, every month of 2025. Hà Nội’s dry winter (Nov–Apr) is the worst stretch anywhere, and every city’s cleanest month falls between July and October. Sa Pa has no monitor nearby.

Monthly US AQI, 2025

Select a cell to set the month; select a city name for its profile.

Good ≤50Moderate ≤100Unhealthy for sensitive groups ≤150Unhealthy ≤200
JanFebMarAprMayJunJulAugSepOctNovDec2025 avgSa Pano monitor nearbyNo IQAir monitor nearby · climate onlyHà Nội180154153152897882727892122169127Hạ Longdata from Mar––621477058645858698015181Huế80556767533829232129596056Đà Nẵng95647182604233383851627062Nha Trang≈ via Qui Nhon≈74≈54≈71≈74≈57≈56≈52≈60≈53≈55≈62≈62≈60Đà Lạt76593865555244563341455655Vũng Tàu≈ via Phan Thiet≈63≈61≈62≈59≈36≈55≈57≈54≈33≈25≈57≈57≈55Hồ Chí Minh City109847569626762626073789374
Source: IQAir monthly city averages [1]; categories US EPA 2024 breakpoints [5]≈ = nearby stand-in city · – = no IQAir data · 2025 avg is IQAir's annual figure

Compare cities

One measure at a time, on one axis. Select names in the legend to add or remove lines; hover the chart to read every line in that month, or a legend entry to pick out one.

Monthly US AQI, 2025

GoodModerateUnhealthy for sensitive groupsUnhealthy050100150200JanFebMarAprMayJunJulAugSepOctNovDecHà Nội 169Hồ Chí Minh City 93Đà Nẵng 70
Source: IQAir [1]; category bands US EPA [5]

Climate at a glance

Average daily low-to-high range, relative humidity and rainfall by month. Every panel shares the same scales, so you can compare across cities.

Daily temperature range (°C), humidity and rain

Top: bars run from the average daily low to the average daily high. Middle: relative humidity. Bottom: monthly rainfall in mm. Hover any panel to read another month everywhere.

Oct 19°/14° · 91% · 201 mm
Station: Sa Pa (1,570 m)
10°20°30°70%90%400800mmJFMAMJJASOND
Oct 30°/23° · 79% · 155 mm
Station: Láng, Đống Đa (downtown)
10°20°30°70%90%400800mmJFMAMJJASOND
Oct 29°/22° · 79% · 143 mm
Station: Bãi Cháy
10°20°30°70%90%400800mmJFMAMJJASOND
Oct 29°/23° · 88% · 773 mm
Station: Huế
10°20°30°70%90%400800mmJFMAMJJASOND
Oct 30°/24° · 84% · 628 mm
Station: Đà Nẵng
10°20°30°70%90%400800mmJFMAMJJASOND
Oct 30°/24° · 83% · 312 mm
Station: Nha Trang
10°20°30°70%90%400800mmJFMAMJJASOND
Oct 23°/15° · 89% · 245 mm
Station: Đà Lạt (1,513 m)
10°20°30°70%90%400800mmJFMAMJJASOND
Oct 31°/25° · 84% · 240 mm
Station: Vũng Tàu
10°20°30°70%90%400800mmJFMAMJJASOND
Oct 32°/25° · 84% · 240 mm
Station: Tân Sơn Nhất Airport
10°20°30°70%90%400800mmJFMAMJJASOND
Source: IBST station normals [2], transcribed from Wikipedia climate tables [3]; Ho Chi Minh City rainfall WMO [4]Station names are listed under each city

Sources & method

Every number on this page traces back to one of these. Numbered markers like [1] throughout the page link here.

  1. [1]
    World's most polluted cities — historical data, 2017–2025
    IQAir (AirVisual)
    Monthly and annual PM2.5 averages with IQAir’s US AQI conversion, from the 2025 World Air Quality Report dataset (published 31 Mar 2026). Monthly values are for 2025, the only year IQAir breaks out by month. Retrieved 29 Oct 2026; Ha Long added 30 Oct 2026.
  2. [2]
    QCVN 02:2022/BXD — Natural physical and climatic data for construction
    Vietnam Institute for Building Science and Technology (IBST) / Ministry of Construction
    Long-term station normals for mean daily maximum and minimum temperature, mean relative humidity and mean monthly rainfall. Cited by the Wikipedia climate tables used here.
  3. [3]
    Climate tables for each city
    Wikipedia
    Station values transcribed from the “Climate data” box of each city’s article. Links below point at the exact revision read on 29 Oct 2026 (Ha Long and Sa Pa on 30 Oct 2026, from the articles on the former city and town, since 2025’s administrative reforms moved the climate tables there).
  4. [4]
    World Weather Information Service — Ho Chi Minh City climate (1991–2020)
    World Meteorological Organization / Viet Nam Meteorological and Hydrological Administration
    Mean monthly rainfall at Tân Sơn Nhất. Used for Ho Chi Minh City only: the Wikipedia table cites WMO for rain but reads 490 mm for September and 340 mm for October, where WMO gives 273 and 240. Retrieved 29 Oct 2026.
  5. [5]
    Technical Assistance Document for the Reporting of Daily Air Quality — the AQI (EPA-454/B-24-002)
    US Environmental Protection Agency, May 2024
    AQI categories and the 2024 PM2.5 breakpoints (Good ≤ 9.0, Moderate ≤ 35.4, Unhealthy for sensitive groups ≤ 55.4, Unhealthy ≤ 125.4 µg/m³).
  6. [6]
    WHO global air quality guidelines (2021)
    World Health Organization
    Annual PM2.5 guideline of 5 µg/m³, shown as a reference line on the yearly trend.
  7. [7]
    Historical Weather API (ERA5 reanalysis)
    Open-Meteo / ECMWF Copernicus
    Used only as a cross-check: 2015–2024 monthly means agree with the station normals within 2.3 °C in every month and city. Rainfall follows the same seasonal shape and peaks in the same month in seven of nine cities, but annual totals differ by −19% to +57% (wetter in seven cities, drier at Ha Long and Sa Pa).
  8. [8]
    Admin-0 countries, 1:50m
    Natural Earth, via the world-atlas package
    Country outlines for the map. Offshore islands outside the map frame are not drawn.

How the numbers were put together

  • Air quality is 2025 only. IQAir publishes a monthly breakdown just for its latest report year. Yearly averages for Hanoi and Ho Chi Minh City have been steady since 2017 (AQI 103–129 and 70–84), so 2025 is a fair picture of a typical year.
  • AQI is IQAir’s conversion of each month’s mean PM2.5 using the US EPA 2024 breakpoints. Recomputing it from PM2.5 reproduces all 119 of IQAir’s figures for the other cities, and Ha Long’s AQI was computed the same way from its PM2.5. It describes the monthly average, not how bad the worst days get.
  • Two cities use stand-ins. IQAir has no monitors in Nha Trang or Vung Tau. Their air figures come from Qui Nhon (170 km away) and Phan Thiet (130 km away), and are marked ≈ everywhere. A modelled alternative (Open-Meteo’s CAMS air-quality model) was tested and rejected: where it can be compared with monitors, it roughly doubled rainy-season readings.
  • Two cities have gaps. IQAir has no monitors in Sa Pa or anywhere in the northwest highlands; the nearest city it tracks, Vinh Yen, is a lowland delta city about 210 km away, so Sa Pa shows climate only rather than a misleading stand-in. Ha Long’s data starts in March 2025, so its January and February are blank and its 2025 average covers March to December.
  • Small cities have few monitors. Da Lat, Hue, Ha Long, Qui Nhon and Phan Thiet rely on a handful of sensors, so month-to-month swings are partly noise. IQAir has no history for Da Lat or Ha Long before 2025, and Hue’s yearly average has jumped around (120 in 2022, 47 in 2023).
  • Climate is a long-term normal, not 2025 weather: average daily high, average daily low and mean relative humidity at each city’s main weather station. Monthly means from ERA5 reanalysis for 2015–2024 agree within 2.3 °C in every month and city.
  • Rainfall is the long-term monthly mean at the same stations. One correction: the Ho Chi Minh City table on Wikipedia cites the World Meteorological Organization for rain but has September and October wrong (490 and 340 mm), so those figures come straight from WMO (273 and 240 mm). ERA5 rain matches the seasonal pattern, but annual totals differ by −19% to +57% (wetter in seven cities, drier at Ha Long and Sa Pa), so it is not used for the numbers.
  • Temperatures and rainfall are rounded to whole numbers on screen; the downloads keep one decimal.

Weather stations

  • Hà Nội: Láng, Đống Đa (downtown) (1991–2020 normals) · table
  • Hồ Chí Minh City: Tân Sơn Nhất Airport · table
  • Đà Nẵng: Đà Nẵng · table
  • Huế: Huế · table
  • Nha Trang: Nha Trang · table
  • Đà Lạt: Đà Lạt (1,513 m) · table
  • Vũng Tàu: Vũng Tàu · table
  • Hạ Long: Bãi Cháy · table
  • Sa Pa: Sa Pa (1,570 m) · table

Download the data

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