SmogRank / Thailand / Loei / Loei

Loei, month by month

Loei has a measured daily mean on 677 days since 1 January 2023. Its worst month was April 2026, at 159 US AQI (66.8 µg/m³), 27th of 2,941 cities on that month's world ranking. Its cleanest was August 2026, at 41 US AQI (7.4 µg/m³).

Every month since 2023

202683 so far213 days measured240th of 2,791 in the world
Jan98#133Feb85#303Mar99#189Apr159#27May59#492Jun47#933Jul2 daysAug41#1,911Sep14 daysOctnone
2025too few days for a mean (a year needs 256)194 days measured
Jan5 daysFeb93#190Mar141#76Apr85#198May47#1,227Jun47#1,720JulnoneAug6 daysSep13 daysOctnoneNov11 daysDec73#474
2024too few days for a mean (a year needs 257)185 days measured
Jan21 daysFeb130#34Mar18 daysApr146#26May76#112Jun44#1,358Jul18 daysAug17 daysSep5 daysOctnoneNovnoneDecnone
2023too few days for a mean (a year needs 256)85 days measured
Jan89#67Feb2 daysMar8 daysApr18 daysMay15 daysJun10 daysJul5 daysAug2 daysSep2 daysOctnoneNovnoneDecnone
Each square is a month's mean PM2.5 in US AQI from Loei'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 Loei 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

28 months
MonthWhy
Oct 2026No day measured. The others: 11 with no readings from the monitor, 1 with under 18 hours of readings or readings that failed our checks.
Sep 202614 of 30 days measured; a month needs 21. The others: 14 with no readings from the monitor, 1 with readings for part of the day (a day needs 18 hours), 1 with under 18 hours of readings or readings that failed our checks.
Jul 20262 of 31 days measured; a month needs 22. The others: 29 with under 18 hours of readings or readings that failed our checks.
Nov 202511 of 30 days measured; a month needs 21. The others: 19 with under 18 hours of readings or readings that failed our checks.
Oct 2025No day measured. The others: 31 with under 18 hours of readings or readings that failed our checks.
Sep 202513 of 30 days measured; a month needs 21. The others: 17 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.
Jan 20255 of 31 days measured; a month needs 22. The others: 26 with under 18 hours of readings or readings that failed our checks.
Dec 2024No day measured. The others: 31 with under 18 hours of readings or readings that failed our checks.
Nov 2024No day measured. The others: 30 with under 18 hours of readings or readings that failed our checks.
Oct 2024No day measured. The others: 31 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 202417 of 31 days measured; a month needs 22. The others: 14 with under 18 hours of readings or readings that failed our checks.
Jul 202418 of 31 days measured; a month needs 22. The others: 13 with under 18 hours of readings or readings that failed our checks.
Mar 202418 of 31 days measured; a month needs 22. The others: 13 with under 18 hours of readings or readings that failed our checks.
Jan 202421 of 31 days measured; a month needs 22. The others: 10 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 20232 of 31 days measured; a month needs 22. The others: 29 with under 18 hours of readings or readings that failed our checks.
Jul 20235 of 31 days measured; a month needs 22. The others: 1 missing from OpenAQ's archive, 25 with under 18 hours of readings or readings that failed our checks.
Jun 202310 of 30 days measured; a month needs 21. The others: 20 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 20238 of 31 days measured; a month needs 22. The others: 19 missing from OpenAQ's archive, 4 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.

Loei's worst months

MonthUS AQIDays measuredWorld rankEpisode
April 2026 15966.8 µg/m³28 of 3027thof 2,941Northern Thailand and Laos, April 2026
April 2024 14653.8 µg/m³28 of 3026thof 2,520Thailand and Laos, April and May 2024
March 2025 14151.6 µg/m³28 of 3176thof 2,862Thailand and Laos, March 2025
February 2024 13047.3 µg/m³21 of 2934thof 2,486Thailand, February 2024
March 2026 9934.9 µg/m³30 of 31189thof 2,971–
January 2026 9834.1 µg/m³29 of 31133rdof 2,617–

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.

Loei's worst days

DayUS AQIEpisode
7 Apr 2023 290215.0 µg/m³Northern Thailand and Laos around Bangkok, 5 to 8 April 2023
8 Apr 2023 287212.0 µg/m³Northern Thailand and Laos around Bangkok, 5 to 8 April 2023
26 Mar 2025 207132.0 µg/m³Thailand and Laos, March 2025
7 Mar 2024 205130.0 µg/m³Northern Thailand and Laos, March 2024
25 Mar 2025 200125.0 µg/m³Thailand and Laos, March 2025
28 Mar 2023 196119.0 µg/m³Northern Thailand and Laos, March and April 2023
24 Mar 2025 190111.0 µg/m³Thailand and Laos, March 2025
5 Apr 2024 188108.0 µg/m³–
5 Apr 2023 185104.0 µg/m³Northern Thailand and Laos around Bangkok, 5 to 8 April 2023
Northern Thailand and Laos around Chiang Mai, 5 April 2023
17 Apr 2026 185104.0 µg/m³Northern Thailand and Laos, April 2026

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, Loei, Thailand, 1 Jan 2023 – 14 Sep 2026. Monitor data from Air4Thai via OpenAQ; sources listed at smogrank.com/sources. smogrank.com/th/loei/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.

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

Updated 2026-10-12 18:07 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).