SmogRank / Thailand / Phra Nakhon Si Ayutthaya / Phra Nakhon Si Ayutthaya

Phra Nakhon Si Ayutthaya, month by month

Phra Nakhon Si Ayutthaya has a measured daily mean on 708 days since 1 January 2023. Its worst month was January 2024, at 116 US AQI (41.5 µg/m³), 61st of 2,385 cities on that month's world ranking. Its cleanest was September 2025, at 43 US AQI (7.7 µg/m³).

Every month since 2023

202671 so far240 days measured357th of 2,798 in the world
Jan97#135Feb84#325Mar78#479Apr87#252May59#486Jun51#790Jul3 daysAug50#1,181Sep60#408Oct71#106
2025too few days for a mean (a year needs 256)215 days measured
Jan5 daysFeb99#153Mar95#248Apr90#170May21 daysJun52#1,450JulnoneAug6 daysSep43#1,388Oct10 daysNov10 daysDec78#385
2024too few days for a mean (a year needs 257)172 days measured
Jan116#61Feb20 daysMar19 daysApr92#73May19 daysJun55#414Jul16 daysAug12 daysSep2 daysOct2 daysNov3 daysDecnone
2023too few days for a mean (a year needs 256)81 days measured
Jan19 daysFeb2 daysMar8 daysApr19 daysMay15 daysJun9 daysJul4 daysAug3 daysSep2 daysOctnoneNovnoneDecnone
Each square is a month's mean PM2.5 in US AQI from Phra Nakhon Si Ayutthaya'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 Phra Nakhon Si Ayutthaya marked; each year, the year's. A dashed square is the running month, so far.
Good0–50
Moderate51–100
Unhealthy for 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
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 202510 of 30 days measured; a month needs 21. The others: 20 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 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 20242 of 30 days measured; a month needs 21. The others: 28 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 202416 of 31 days measured; a month needs 22. The others: 15 with under 18 hours of readings or readings that failed our checks.
May 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 202419 of 31 days measured; a month needs 22. The others: 12 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.
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 20233 of 31 days measured; a month needs 22. The others: 28 with under 18 hours of readings or readings that failed our checks.
Jul 20234 of 31 days measured; a month needs 22. The others: 1 missing from OpenAQ's archive, 26 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 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 202319 of 30 days measured; a month needs 21. The others: 2 missing from OpenAQ's archive, 9 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.
Jan 202319 of 31 days measured; a month needs 22. The others: 6 missing from OpenAQ's archive, 6 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.

Phra Nakhon Si Ayutthaya's worst months

MonthUS AQIDays measuredWorld rankEpisode
January 2024 11641.5 µg/m³24 of 3161stof 2,385–
February 2025 9935.1 µg/m³28 of 28153rdof 2,633–
January 2026 9733.9 µg/m³31 of 31135thof 2,617–
March 2025 9532.5 µg/m³28 of 31248thof 2,862Thailand and Laos, March 2025
April 2024 9231.0 µg/m³29 of 3073rdof 2,520Thailand and Laos, April and May 2024
April 2025 9029.8 µg/m³21 of 30170thof 2,951–

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.

Phra Nakhon Si Ayutthaya's worst days

DayUS AQIEpisode
24 Jan 2025 17386.4 µg/m³Northern Thailand, January 2025
1 Feb 2023 16575.4 µg/m³Northern Thailand and Laos, January and February 2023
14 Feb 2024 16169.1 µg/m³Thailand, February 2024
15 Feb 2024 16068.8 µg/m³Thailand, February 2024
2 Apr 2025 15966.9 µg/m³–
25 Jan 2025 15966.8 µg/m³Northern Thailand, January 2025
24 Mar 2025 15663.3 µg/m³Thailand and Laos, March 2025
29 Mar 2025 15560.7 µg/m³Thailand and Laos, March 2025
23 Mar 2025 15560.6 µg/m³Thailand and Laos, March 2025
16 Apr 2023 15460.1 µg/m³Thailand, 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, Phra Nakhon Si Ayutthaya, Thailand, 1 Jan 2023 – 12 Oct 2026. Monitor data from Air4Thai via OpenAQ; sources listed at smogrank.com/sources. smogrank.com/th/phra-nakhon-si-ayutthaya/history (accessed 13 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.

Phra Nakhon Si Ayutthaya now: the last 24 hours, its ranks today and the last 12 months day by day.

Updated 2026-10-13 04:07 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).