SmogRank / Thailand / Prachin Buri / Si Maha Phot

Si Maha Phot, month by month

Si Maha Phot has a measured daily mean on 683 days since 1 January 2023. Its worst month was February 2025, at 120 US AQI (43.4 µg/m³), 67th of 2,633 cities on that month's world ranking. Its cleanest was September 2025, at 61 US AQI (14.4 µg/m³).

Every month since 2023

202680 so far236 days measured261st of 2,793 in the world
Jan103#113Feb97#210Mar89#286Apr90#225May72#274Jun63#319Jul3 daysAug67#303Sep66#318Oct69#118
2025too few days for a mean (a year needs 256)202 days measured
Jan5 daysFeb120#67Mar106#187Apr85#203May20 daysJun67#293JulnoneAug5 daysSep61#359Oct10 daysNov11 daysDec76#428
2024too few days for a mean (a year needs 257)167 days measured
Jan15 daysFeb20 daysMar18 daysApr90#74May73#135Jun63#197Jul13 daysAug12 daysSep3 daysOct2 daysNov3 daysDecnone
2023too few days for a mean (a year needs 256)78 days measured
Jan86#76Feb1 dayMar8 daysApr17 daysMay14 daysJun9 daysJul3 daysAug2 daysSep2 daysOctnoneNovnoneDecnone
Each square is a month's mean PM2.5 in US AQI from Si Maha Phot'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 Si Maha Phot marked; each year, the year's. A dashed square is the running month, so far.
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

27 months
MonthWhy
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 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 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 20255 of 31 days measured; a month needs 22. The others: 26 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 202520 of 31 days measured; a month needs 22. The others: 11 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 20243 of 30 days measured; a month needs 21. The others: 27 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 20243 of 30 days measured; a month needs 21. The others: 27 with under 18 hours of readings or readings that failed our checks.
Aug 202412 of 31 days measured; a month needs 22. The others: 19 with under 18 hours of readings or readings that failed our checks.
Jul 202413 of 31 days measured; a month needs 22. The others: 18 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.
Feb 202420 of 29 days measured; a month needs 21. The others: 1 missing from OpenAQ's archive, 8 with under 18 hours of readings or readings that failed our checks.
Jan 202415 of 31 days measured; a month needs 22. The others: 16 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 20233 of 31 days measured; a month needs 22. The others: 1 missing from OpenAQ's archive, 27 with under 18 hours of readings or readings that failed our checks.
Jun 20239 of 30 days measured; a month needs 21. The others: 21 with under 18 hours of readings or readings that failed our checks.
May 202314 of 31 days measured; a month needs 22. The others: 17 with under 18 hours of readings or readings that failed our checks.
Apr 202317 of 30 days measured; a month needs 21. The others: 2 missing from OpenAQ's archive, 11 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 20231 of 28 days measured; a month needs 20. The others: 25 missing from OpenAQ's archive, 2 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.

Si Maha Phot's worst months

MonthUS AQIDays measuredWorld rankEpisode
February 2025 12043.4 µg/m³27 of 2867thof 2,633–
March 2025 10637.5 µg/m³24 of 31187thof 2,862Thailand and Laos, March 2025
January 2026 10336.4 µg/m³29 of 31113thof 2,617–
February 2026 9733.6 µg/m³27 of 28210thof 2,866–
April 2024 9030.3 µg/m³28 of 3074thof 2,520–
April 2026 9030.2 µg/m³28 of 30225thof 2,941–

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.

Si Maha Phot's worst days

DayUS AQIEpisode
25 Jan 2025 18096.5 µg/m³Northern Thailand, January 2025
24 Jan 2025 17487.8 µg/m³Northern Thailand, January 2025
15 Feb 2024 17083.2 µg/m³Thailand, February 2024
24 Mar 2025 16880.4 µg/m³Thailand and Laos, March 2025
26 Jan 2025 16677.3 µg/m³Northern Thailand, January 2025
2 Feb 2025 15966.6 µg/m³–
25 Mar 2025 15764.7 µg/m³Thailand and Laos, March 2025
22 Jan 2024 15764.5 µg/m³–
14 Feb 2024 15764.0 µg/m³Thailand, February 2024
1 Feb 2025 15663.0 µg/m³–

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, Si Maha Phot, Thailand, 1 Jan 2023 – 12 Oct 2026. Monitor data from Air4Thai via OpenAQ; sources listed at smogrank.com/sources. smogrank.com/th/si-maha-phot/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.

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

Updated 2026-10-12 23:07 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).