SmogRank / Thailand / Chiang Rai / Chiang Rai

Chiang Rai, month by month

Chiang Rai has a measured daily mean on 743 days since 1 January 2023. Its worst month was April 2026, at 177 US AQI (92.4 µg/m³), 9th of 2,941 cities on that month's world ranking. Its cleanest was September 2025, at 48 US AQI (8.7 µg/m³).

Every month since 2023

202685 so far247 days measured226th of 2,791 in the world
Jan78#286Feb78#436Mar125#109Apr177#9May59#486Jun51#790Jul3 daysAug49#1,258Sep52#669Oct7 days
2025too few days for a mean (a year needs 256)217 days measured
Jan4 daysFeb88#223Mar146#69Apr115#79May21 daysJun49#1,627JulnoneAug6 daysSep48#985Oct10 daysNov12 daysDec81#364
2024too few days for a mean (a year needs 257)202 days measured
Jan83#163Feb99#80Mar20 daysApr157#12May112#43Jun52#700Jul19 daysAug18 daysSep5 daysOct2 daysNov4 daysDec1 day
2023too few days for a mean (a year needs 256)77 days measured
Jan99#47Feb2 daysMar9 daysApr18 daysMay15 daysJun7 daysJul1 dayAug1 daySep2 daysOctnoneNovnoneDecnone
Each square is a month's mean PM2.5 in US AQI from Chiang Rai's measured days, with its place on that month's world ranking under it. A month has a mean once 70% of its days are measured, the rule the monthly rankings use; under that, the square gives the days measured. Each square opens that month's ranking with Chiang Rai marked; each year, the year's.
Good0–50
Moderate51–100
Sensitive groups101–150
Unhealthy151–200
Very unhealthy201–300
Hazardous301+

The US EPA's Air Quality Index for PM2.5 (2024 breakpoints). Show values as: µg/m³ · US AQI · India AQI · China AQI · European AQI · UK DAQI · Canada AQHI+. About the scales

Months without a mean, and why

26 months
MonthWhy
Oct 20267 of 12 days measured; a month needs 9. The others: 5 with no readings from the monitor.
Jul 20263 of 31 days measured; a month needs 22. The others: 28 with under 18 hours of readings or readings that failed our checks.
Nov 202512 of 30 days measured; a month needs 21. The others: 18 with under 18 hours of readings or readings that failed our checks.
Oct 202510 of 31 days measured; a month needs 22. The others: 21 with under 18 hours of readings or readings that failed our checks.
Aug 20256 of 31 days measured; a month needs 22. The others: 25 with under 18 hours of readings or readings that failed our checks.
Jul 2025No day measured. The others: 31 with under 18 hours of readings or readings that failed our checks.
May 202521 of 31 days measured; a month needs 22. The others: 10 with under 18 hours of readings or readings that failed our checks.
Jan 20254 of 31 days measured; a month needs 22. The others: 27 with under 18 hours of readings or readings that failed our checks.
Dec 20241 of 31 days measured; a month needs 22. The others: 30 with under 18 hours of readings or readings that failed our checks.
Nov 20244 of 30 days measured; a month needs 21. The others: 26 with under 18 hours of readings or readings that failed our checks.
Oct 20242 of 31 days measured; a month needs 22. The others: 29 with under 18 hours of readings or readings that failed our checks.
Sep 20245 of 30 days measured; a month needs 21. The others: 25 with under 18 hours of readings or readings that failed our checks.
Aug 202418 of 31 days measured; a month needs 22. The others: 13 with under 18 hours of readings or readings that failed our checks.
Jul 202419 of 31 days measured; a month needs 22. The others: 12 with under 18 hours of readings or readings that failed our checks.
Mar 202420 of 31 days measured; a month needs 22. The others: 11 with under 18 hours of readings or readings that failed our checks.
Dec 2023No day measured. The others: 31 with under 18 hours of readings or readings that failed our checks.
Nov 2023No day measured. The others: 30 with under 18 hours of readings or readings that failed our checks.
Oct 2023No day measured. The others: 31 with under 18 hours of readings or readings that failed our checks.
Sep 20232 of 30 days measured; a month needs 21. The others: 28 with under 18 hours of readings or readings that failed our checks.
Aug 20231 of 31 days measured; a month needs 22. The others: 30 with under 18 hours of readings or readings that failed our checks.
Jul 20231 of 31 days measured; a month needs 22. The others: 1 missing from OpenAQ's archive, 29 with under 18 hours of readings or readings that failed our checks.
Jun 20237 of 30 days measured; a month needs 21. The others: 23 with under 18 hours of readings or readings that failed our checks.
May 202315 of 31 days measured; a month needs 22. The others: 16 with under 18 hours of readings or readings that failed our checks.
Apr 202318 of 30 days measured; a month needs 21. The others: 2 missing from OpenAQ's archive, 10 with under 18 hours of readings or readings that failed our checks.
Mar 20239 of 31 days measured; a month needs 22. The others: 19 missing from OpenAQ's archive, 3 with under 18 hours of readings or readings that failed our checks.
Feb 20232 of 28 days measured; a month needs 20. The others: 25 missing from OpenAQ's archive, 1 with under 18 hours of readings or readings that failed our checks.

A day counts once 18 hours of it are measured; a month needs 70% of its days.

Chiang Rai's worst months

MonthUS AQIDays measuredWorld rankEpisode
April 2026 17792.4 µg/m³30 of 309thof 2,941Northern Thailand and Laos, April 2026
Northern Thailand and Laos, March and April 2026
April 2024 15764.6 µg/m³27 of 3012thof 2,520Thailand and Laos, April and May 2024
March 2025 14653.6 µg/m³28 of 3169thof 2,862–
March 2026 12545.4 µg/m³28 of 31109thof 2,971Northern Thailand and Laos, March and April 2026
April 2025 11541.3 µg/m³23 of 3079thof 2,951–
May 2024 11240.1 µg/m³30 of 3143rdof 2,684Northern Thailand and Laos, May 2024
Thailand and Laos, April and May 2024

Monthly means over the days measured; finished months only. World rank: its place on that month's world ranking of every city with enough days. Each month opens that ranking.

Chiang Rai's worst days

DayUS AQIEpisode
28 Mar 2023 500+348.0 µg/m³Northern Thailand and Laos, March and April 2023
27 Mar 2023 408279.0 µg/m³Northern Thailand and Laos, March and April 2023
1 Apr 2023 372261.0 µg/m³Northern Thailand and Laos, March and April 2023
31 Mar 2023 362256.0 µg/m³Northern Thailand and Laos, March and April 2023
30 Mar 2023 326238.0 µg/m³Northern Thailand and Laos, March and April 2023
7 Apr 2023 306228.0 µg/m³Northern Thailand and Laos around Bangkok, 5 to 8 April 2023
8 Apr 2023 304227.0 µg/m³Northern Thailand and Laos around Bangkok, 5 to 8 April 2023
26 Mar 2023 292217.0 µg/m³Northern Thailand and Laos, March and April 2023
2 Apr 2023 277202.0 µg/m³Northern Thailand and Laos, March and April 2023
29 Mar 2023 268193.0 µg/m³Northern Thailand and Laos, March and April 2023

Daily means, the highest since 1 Jan 2023; the WHO's daily guideline is 15 µg/m³. Each date opens that day's world ranking, and each episode the bad-air spell it was part of.

Use this history

SmogRank, PM2.5 monthly and daily means, Chiang Rai, Thailand, 1 Jan 2023 – 7 Oct 2026. Monitor data from Air4Thai via OpenAQ; sources listed at smogrank.com/sources. smogrank.com/th/chiang-rai/history (accessed 12 Oct 2026).

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You're welcome to reuse a single chart, image or figure with this citation and a link. Terms. Raw monitor readings in bulk are published by OpenAQ, under each provider's licence.

Chiang Rai now: the last 24 hours, its ranks today and the last 12 months day by day.

Updated 2026-10-12 20:07 UTC. Values are PM2.5 (fine particles), the median of each city's monitors, as the US AQI PM2.5 sub-index. Some low-cost readings: Sensor.Community, ODbL (data and licence). Some readings: Uzhydromet (Uzbekistan's Hydrometeorological Service); Department of Environment, Nepal; Vietnam's government monitors; Aurassure; Umhverfisstofnun (Environment Agency of Iceland); RMCAB (Secretaría Distrital de Ambiente, Bogotá); Love My Air (City and County of Denver), no reuse terms published (why we use them).