SmogRank / Episodes / Thailand
Thailand and Laos, January and February 2023
For 2 days, from 31 January to 1 February 2023, 34 cities in Thailand and Laos had PM2.5 at least twice their usual for the time of year. The worst reading was Tha Bo, Nong Khai, Thailand: 122.0 µg/m³ on 1 February, about 2.6× its usual 47.0.
No cause named We have no fire or smoke records for these days, so we only say what the measurements show.
Cities reached 34 in 2 countries
Days 2 31 January to 1 February 2023
Worst day 1 February 34 cities counted
Furthest above usual 3.2× Sakon Nakhon
Day by day
Play 1 February 34 cities at twice their usual or more
Chaiyaphum Phetchabun Kalasin Nakhon Ratchasima Phichit Nakhon Sawan Lop Buri Saraburi Sing Buri Si Maha Phot Kamphaeng Phet Nan Aranyaprathet Khlong Luang Suphan Buri Khlong Sam Wa Khan Na Yao Ubon Ratchathani Bueng Kum Mueang Nonthaburi Tak Bang Kapi Bang Khun Thian Kanchanaburi Ban Talat Bueng Laem Chabang Mae Sot Ratchaburi Lamphun Chanthaburi Ban Chang Chiang Mai Trat Mae Sai Bang Bo District Sai Mai Uttaradit Nong Chok Phrae Lak Si Lat Krabang Roi Et Phra Pradaeng Phra Nakhon Si Ayutthaya Saphan Sung Nakhon Pathom Nong Khaem Si Sa Ket Rayong Chiang Rai Bangkok Lampang Hua Hin Buri Ram Sukhothai Samut Sakhon Vientiane Ban Houakhoua Mukdahan Ban Khlong Prawet Ban Samae Dam Bang Na Pakxan Loei Tha Bo Nong Bua Lamphu Udon Thani Sakon Nakhon 28 Jan 29 30 31 1 Feb 2 3 4 Every measured city in the area, coloured by its PM2.5 that day; a dark ring marks a city at twice its usual or more. Bars: cities counted each day, coloured by their median level. Choose a day or press play; without JavaScript, the days link to that day's world ranking.
How it spread
Nong Bua Lamphu Nong Bua Lamphu, 28 January: 20.4 µg/m³ Nong Bua Lamphu, 29 January: 34.2 µg/m³ Nong Bua Lamphu, 30 January: 53.5 µg/m³ Nong Bua Lamphu, 31 January: 81.1 µg/m³, 2.8× its usual 28.7 Nong Bua Lamphu, 1 February: 76.5 µg/m³, 2.7× its usual 28.3 Nong Bua Lamphu, 2 February: no reading Nong Bua Lamphu, 3 February: no reading Nong Bua Lamphu, 4 February: no reading Loei Loei, 28 January: 19.8 µg/m³ Loei, 29 January: 45.0 µg/m³ Loei, 30 January: 60.7 µg/m³ Loei, 31 January: 77.4 µg/m³, 2.3× its usual 34.1 Loei, 1 February: 88.9 µg/m³, 2.6× its usual 33.8 Loei, 2 February: no reading Loei, 3 February: no reading Loei, 4 February: no reading Sukhothai Sukhothai, 28 January: 53.0 µg/m³ Sukhothai, 29 January: 55.5 µg/m³ Sukhothai, 30 January: 67.4 µg/m³ Sukhothai, 31 January: 72.2 µg/m³, 2.0× its usual 35.6 Sukhothai, 1 February: 81.0 µg/m³, 2.3× its usual 34.9 Sukhothai, 2 February: no reading Sukhothai, 3 February: no reading Sukhothai, 4 February: no reading Udon Thani Udon Thani, 28 January: 17.3 µg/m³ Udon Thani, 29 January: 32.3 µg/m³ Udon Thani, 30 January: 44.2 µg/m³ Udon Thani, 31 January: 60.7 µg/m³, 2.3× its usual 26.4 Udon Thani, 1 February: 76.3 µg/m³, 2.9× its usual 26.5 Udon Thani, 2 February: no reading Udon Thani, 3 February: no reading Udon Thani, 4 February: no reading Pakxan Pakxan, 28 January: 21.3 µg/m³ Pakxan, 29 January: 36.3 µg/m³ Pakxan, 30 January: 41.9 µg/m³ Pakxan, 31 January: 58.3 µg/m³, 2.5× its usual 23.1 Pakxan, 1 February: 63.8 µg/m³, 2.5× its usual 25.5 Pakxan, 2 February: no reading Pakxan, 3 February: no reading Pakxan, 4 February: no reading Sakon Nakhon Sakon Nakhon, 28 January: 16.7 µg/m³ Sakon Nakhon, 29 January: 25.4 µg/m³ Sakon Nakhon, 30 January: 32.5 µg/m³ Sakon Nakhon, 31 January: 44.5 µg/m³, 2.4× its usual 18.7 Sakon Nakhon, 1 February: 62.0 µg/m³, 3.2× its usual 19.5 Sakon Nakhon, 2 February: no reading Sakon Nakhon, 3 February: no reading Sakon Nakhon, 4 February: no reading Tha Bo Tha Bo, 28 January: 35.8 µg/m³ Tha Bo, 29 January: 50.2 µg/m³ Tha Bo, 30 January: 90.5 µg/m³ Tha Bo, 31 January: 92.7 µg/m³ Tha Bo, 1 February: 122.0 µg/m³, 2.6× its usual 47.0 Tha Bo, 2 February: no reading Tha Bo, 3 February: no reading Tha Bo, 4 February: no reading Vientiane Vientiane, 28 January: 35.8 µg/m³ Vientiane, 29 January: 50.2 µg/m³ Vientiane, 30 January: 90.5 µg/m³ Vientiane, 31 January: 92.7 µg/m³ Vientiane, 1 February: 122.0 µg/m³, 2.3× its usual 54.1 Vientiane, 2 February: no reading Vientiane, 3 February: no reading Vientiane, 4 February: no reading Bang Na Bang Na, 28 January: 34.5 µg/m³ Bang Na, 29 January: 26.7 µg/m³ Bang Na, 30 January: 36.1 µg/m³ Bang Na, 31 January: 57.0 µg/m³ Bang Na, 1 February: 98.5 µg/m³, 2.4× its usual 40.4 Bang Na, 2 February: no reading Bang Na, 3 February: no reading Bang Na, 4 February: no reading Lampang Lampang, 28 January: 67.2 µg/m³ Lampang, 29 January: 60.4 µg/m³ Lampang, 30 January: 62.9 µg/m³ Lampang, 31 January: 77.4 µg/m³ Lampang, 1 February: 88.7 µg/m³, 2.2× its usual 41.2 Lampang, 2 February: no reading Lampang, 3 February: no reading Lampang, 4 February: no reading Ban Samae Dam Ban Samae Dam, 28 January: 34.1 µg/m³ Ban Samae Dam, 29 January: 25.4 µg/m³ Ban Samae Dam, 30 January: 32.7 µg/m³ Ban Samae Dam, 31 January: 58.9 µg/m³ Ban Samae Dam, 1 February: 88.5 µg/m³, 2.4× its usual 36.7 Ban Samae Dam, 2 February: no reading Ban Samae Dam, 3 February: no reading Ban Samae Dam, 4 February: no reading Nong Khaem Nong Khaem, 28 January: 43.5 µg/m³ Nong Khaem, 29 January: 30.2 µg/m³ Nong Khaem, 30 January: 36.7 µg/m³ Nong Khaem, 31 January: 66.2 µg/m³ Nong Khaem, 1 February: 85.6 µg/m³, 2.1× its usual 41.6 Nong Khaem, 2 February: no reading Nong Khaem, 3 February: no reading Nong Khaem, 4 February: no reading Samut Sakhon Samut Sakhon, 28 January: 44.0 µg/m³ Samut Sakhon, 29 January: 30.6 µg/m³ Samut Sakhon, 30 January: 35.3 µg/m³ Samut Sakhon, 31 January: 67.2 µg/m³ Samut Sakhon, 1 February: 83.1 µg/m³, 2.3× its usual 36.7 Samut Sakhon, 2 February: no reading Samut Sakhon, 3 February: no reading Samut Sakhon, 4 February: no reading Lat Krabang Lat Krabang, 28 January: 32.4 µg/m³ Lat Krabang, 29 January: 25.4 µg/m³ Lat Krabang, 30 January: 40.4 µg/m³ Lat Krabang, 31 January: 57.0 µg/m³ Lat Krabang, 1 February: 82.8 µg/m³, 2.0× its usual 40.9 Lat Krabang, 2 February: no reading Lat Krabang, 3 February: no reading Lat Krabang, 4 February: no reading Nakhon Pathom Nakhon Pathom, 28 January: 37.8 µg/m³ Nakhon Pathom, 29 January: 30.5 µg/m³ Nakhon Pathom, 30 January: 33.3 µg/m³ Nakhon Pathom, 31 January: 60.3 µg/m³ Nakhon Pathom, 1 February: 80.5 µg/m³, 2.1× its usual 38.0 Nakhon Pathom, 2 February: no reading Nakhon Pathom, 3 February: no reading Nakhon Pathom, 4 February: no reading Ban Khlong Prawet Ban Khlong Prawet, 28 January: 29.7 µg/m³ Ban Khlong Prawet, 29 January: 21.8 µg/m³ Ban Khlong Prawet, 30 January: 32.2 µg/m³ Ban Khlong Prawet, 31 January: 48.5 µg/m³ Ban Khlong Prawet, 1 February: 79.7 µg/m³, 2.4× its usual 33.7 Ban Khlong Prawet, 2 February: no reading Ban Khlong Prawet, 3 February: no reading Ban Khlong Prawet, 4 February: no reading Bangkok Bangkok, 28 January: 33.5 µg/m³ Bangkok, 29 January: 26.6 µg/m³ Bangkok, 30 January: 35.1 µg/m³ Bangkok, 31 January: 57.5 µg/m³ Bangkok, 1 February: 78.4 µg/m³, 2.2× its usual 35.4 Bangkok, 2 February: no reading Bangkok, 3 February: no reading Bangkok, 4 February: no reading Saphan Sung Saphan Sung, 28 January: 33.9 µg/m³ Saphan Sung, 29 January: 26.8 µg/m³ Saphan Sung, 30 January: 37.9 µg/m³ Saphan Sung, 31 January: 54.6 µg/m³ Saphan Sung, 1 February: 78.3 µg/m³, 2.1× its usual 37.4 Saphan Sung, 2 February: no reading Saphan Sung, 3 February: no reading Saphan Sung, 4 February: no reading Lak Si Lak Si, 28 January: 39.7 µg/m³ Lak Si, 29 January: 26.2 µg/m³ Lak Si, 30 January: 36.5 µg/m³ Lak Si, 31 January: 59.1 µg/m³ Lak Si, 1 February: 76.7 µg/m³, 2.0× its usual 38.0 Lak Si, 2 February: no reading Lak Si, 3 February: no reading Lak Si, 4 February: no reading Phra Nakhon Si Ayut… Phra Nakhon Si Ayutthaya, 28 January: 31.7 µg/m³ Phra Nakhon Si Ayutthaya, 29 January: 29.5 µg/m³ Phra Nakhon Si Ayutthaya, 30 January: 34.5 µg/m³ Phra Nakhon Si Ayutthaya, 31 January: 51.5 µg/m³ Phra Nakhon Si Ayutthaya, 1 February: 75.4 µg/m³, 2.1× its usual 35.7 Phra Nakhon Si Ayutthaya, 2 February: no reading Phra Nakhon Si Ayutthaya, 3 February: no reading Phra Nakhon Si Ayutthaya, 4 February: no reading Phrae Phrae, 28 January: no reading Phrae, 29 January: no reading Phrae, 30 January: 59.2 µg/m³ Phrae, 31 January: 67.5 µg/m³ Phrae, 1 February: 74.8 µg/m³, 2.0× its usual 36.8 Phrae, 2 February: no reading Phrae, 3 February: no reading Phrae, 4 February: no reading Nong Chok Nong Chok, 28 January: 27.5 µg/m³ Nong Chok, 29 January: 20.3 µg/m³ Nong Chok, 30 January: 38.8 µg/m³ Nong Chok, 31 January: 55.1 µg/m³ Nong Chok, 1 February: 73.7 µg/m³, 2.0× its usual 36.4 Nong Chok, 2 February: no reading Nong Chok, 3 February: no reading Nong Chok, 4 February: no reading Phra Pradaeng Phra Pradaeng, 28 January: 26.8 µg/m³ Phra Pradaeng, 29 January: 21.6 µg/m³ Phra Pradaeng, 30 January: 26.6 µg/m³ Phra Pradaeng, 31 January: 46.5 µg/m³ Phra Pradaeng, 1 February: 73.3 µg/m³, 2.1× its usual 34.3 Phra Pradaeng, 2 February: no reading Phra Pradaeng, 3 February: no reading Phra Pradaeng, 4 February: no reading Uttaradit Uttaradit, 28 January: 45.3 µg/m³ Uttaradit, 29 January: 37.8 µg/m³ Uttaradit, 30 January: 51.8 µg/m³ Uttaradit, 31 January: 58.4 µg/m³ Uttaradit, 1 February: 73.2 µg/m³, 2.0× its usual 36.6 Uttaradit, 2 February: no reading Uttaradit, 3 February: no reading Uttaradit, 4 February: no reading Sai Mai Sai Mai, 28 January: 35.0 µg/m³ Sai Mai, 29 January: 22.3 µg/m³ Sai Mai, 30 January: 36.9 µg/m³ Sai Mai, 31 January: 55.3 µg/m³ Sai Mai, 1 February: 72.4 µg/m³, 2.0× its usual 36.0 Sai Mai, 2 February: no reading Sai Mai, 3 February: no reading Sai Mai, 4 February: no reading Bang Bo District Bang Bo District, 28 January: no reading Bang Bo District, 29 January: 26.4 µg/m³ Bang Bo District, 30 January: no reading Bang Bo District, 31 January: 45.5 µg/m³ Bang Bo District, 1 February: 67.3 µg/m³, 2.0× its usual 33.5 Bang Bo District, 2 February: no reading Bang Bo District, 3 February: no reading Bang Bo District, 4 February: no reading Mukdahan Mukdahan, 28 January: 19.2 µg/m³ Mukdahan, 29 January: 31.3 µg/m³ Mukdahan, 30 January: 36.1 µg/m³ Mukdahan, 31 January: 42.2 µg/m³ Mukdahan, 1 February: 64.8 µg/m³, 2.4× its usual 27.1 Mukdahan, 2 February: no reading Mukdahan, 3 February: no reading Mukdahan, 4 February: no reading Ban Houakhoua Ban Houakhoua, 28 January: 35.2 µg/m³ Ban Houakhoua, 29 January: 26.6 µg/m³ Ban Houakhoua, 30 January: 38.4 µg/m³ Ban Houakhoua, 31 January: 44.1 µg/m³ Ban Houakhoua, 1 February: 63.8 µg/m³, 2.4× its usual 26.4 Ban Houakhoua, 2 February: no reading Ban Houakhoua, 3 February: no reading Ban Houakhoua, 4 February: no reading Chiang Rai Chiang Rai, 28 January: 47.3 µg/m³ Chiang Rai, 29 January: 33.9 µg/m³ Chiang Rai, 30 January: 37.0 µg/m³ Chiang Rai, 31 January: 45.7 µg/m³ Chiang Rai, 1 February: 62.2 µg/m³, 2.2× its usual 28.0 Chiang Rai, 2 February: no reading Chiang Rai, 3 February: no reading Chiang Rai, 4 February: no reading Buri Ram Buri Ram, 28 January: 15.3 µg/m³ Buri Ram, 29 January: 25.4 µg/m³ Buri Ram, 30 January: 33.3 µg/m³ Buri Ram, 31 January: 50.3 µg/m³ Buri Ram, 1 February: 61.1 µg/m³, 2.3× its usual 26.8 Buri Ram, 2 February: no reading Buri Ram, 3 February: no reading Buri Ram, 4 February: no reading Hua Hin Hua Hin, 28 January: 38.9 µg/m³ Hua Hin, 29 January: 25.8 µg/m³ Hua Hin, 30 January: 31.7 µg/m³ Hua Hin, 31 January: 42.8 µg/m³ Hua Hin, 1 February: 60.4 µg/m³, 2.3× its usual 25.9 Hua Hin, 2 February: no reading Hua Hin, 3 February: no reading Hua Hin, 4 February: no reading Rayong Rayong, 28 January: 34.0 µg/m³ Rayong, 29 January: 18.8 µg/m³ Rayong, 30 January: 24.9 µg/m³ Rayong, 31 January: 39.8 µg/m³ Rayong, 1 February: 59.5 µg/m³, 2.2× its usual 27.5 Rayong, 2 February: no reading Rayong, 3 February: no reading Rayong, 4 February: no reading Roi Et Roi Et, 28 January: 12.0 µg/m³ Roi Et, 29 January: 23.6 µg/m³ Roi Et, 30 January: 29.5 µg/m³ Roi Et, 31 January: 42.3 µg/m³ Roi Et, 1 February: 55.2 µg/m³, 2.1× its usual 26.4 Roi Et, 2 February: no reading Roi Et, 3 February: no reading Roi Et, 4 February: no reading Si Sa Ket Si Sa Ket, 28 January: 11.0 µg/m³ Si Sa Ket, 29 January: 19.5 µg/m³ Si Sa Ket, 30 January: 26.8 µg/m³ Si Sa Ket, 31 January: 32.7 µg/m³ Si Sa Ket, 1 February: 52.7 µg/m³, 2.2× its usual 24.1 Si Sa Ket, 2 February: no reading Si Sa Ket, 3 February: no reading Si Sa Ket, 4 February: no reading 28 Jan 29 30 31 1 Feb 2 3 4 Every counted city, in the order the episode reached them, 3 days before to 3 after. Each square is a day, coloured by that day's PM2.5; outlined: at twice the city's usual or more. Good 0–50
Moderate 51–100
Sensitive groups 101–150
Unhealthy 151–200
Very unhealthy 201–300
Hazardous 301+
Every city it reached
City Days Highest Usual Above usual
Sakon Nakhon Sakon Nakhon, Thailand 2 1 February 19.5 3.2× Udon Thani Udon Thani, Thailand 2 1 February 26.5 2.9× Nong Bua Lamphu Nong Bua Lamphu, Thailand 2 31 January 28.7 2.8× Tha Bo Nong Khai, Thailand 1 1 February 47.0 2.6× Loei Loei, Thailand 2 1 February 33.8 2.6× Pakxan Bolikhamsai, Laos 2 1 February 25.5 2.5× Bang Na Bangkok, Thailand 1 1 February 40.4 2.4× Ban Samae Dam Bangkok, Thailand 1 1 February 36.7 2.4× Ban Khlong Prawet Bangkok, Thailand 1 1 February 33.7 2.4× Mukdahan Mukdahan, Thailand 1 1 February 27.1 2.4× Ban Houakhoua Bokeo, Laos 1 1 February 26.4 2.4× Vientiane Vientiane Prefecture, Laos 1 1 February 54.1 2.3× Samut Sakhon Samut Sakhon, Thailand 1 1 February 36.7 2.3× Sukhothai Sukhothai, Thailand 2 1 February 34.9 2.3× Buri Ram Buriram, Thailand 1 1 February 26.8 2.3× Hua Hin Prachuap Khiri Khan, Thailand 1 1 February 25.9 2.3× Lampang Lampang, Thailand 1 1 February 41.2 2.2× Bangkok Bangkok, Thailand 1 1 February 35.4 2.2× Chiang Rai Chiang Rai, Thailand 1 1 February 28.0 2.2× Rayong Rayong, Thailand 1 1 February 27.5 2.2× Si Sa Ket Si Sa Ket, Thailand 1 1 February 24.1 2.2× Nong Khaem Bangkok, Thailand 1 1 February 41.6 2.1× Nakhon Pathom Nakhon Pathom, Thailand 1 1 February 38.0 2.1× Saphan Sung Bangkok, Thailand 1 1 February 37.4 2.1× Phra Nakhon Si Ayutthaya Phra Nakhon Si Ayutthaya, Thailand 1 1 February 35.7 2.1× Phra Pradaeng Samut Prakan, Thailand 1 1 February 34.3 2.1× Roi Et Roi Et, Thailand 1 1 February 26.4 2.1× Lat Krabang Bangkok, Thailand 1 1 February 40.9 2.0× Lak Si Bangkok, Thailand 1 1 February 38.0 2.0× Phrae Phrae, Thailand 1 1 February 36.8 2.0× Nong Chok Bangkok, Thailand 1 1 February 36.4 2.0× Uttaradit Uttaradit, Thailand 1 1 February 36.6 2.0× Sai Mai Bangkok, Thailand 1 1 February 36.0 2.0× Bang Bo District Samut Prakan, Thailand 1 1 February 33.5 2.0×
Daily means in µg/m³, over the days each city counted in this episode. Highest: its highest of those days. Usual: the city's median for the time of year of that day (its days within 21 days of the date, every year, leaving out the week around it). Above usual: its highest day against that, with a usual under 5 µg/m³ taken as 5.
Against other episodes in Thailand and Laos
Number 7 of 23 episodes in Thailand and Laos since our records began, by cities reached.
Thailand and Laos, March 2025 53 Thailand, February 2024 51 Thailand, January 2025 50 Thailand and Laos, April and May 2024 45 Northern Thailand and Laos, 20 to 22 May 2023 41 Thailand, April 2023 35 Thailand and Laos, January and February 2023 34 Northern Thailand and Laos, 16 to 18 May 2023 30 Northern Thailand and Laos, October 2024 24 Thailand and Laos, November and December 2025 22 Thailand, February 2025 17 Northern Thailand, May 2023 17 Bars: cities reached; colour: the level of the episode's highest daily reading. All 23 .
Use this page SmogRank, Thailand and Laos, January and February 2023: 34 cities with PM2.5 at twice their usual or more, 31 January to 1 February 2023, smogrank.com/episodes/2023-01-thailand-and-laos (accessed 4 October 2026).
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You're welcome to reuse a single chart, image or figure with this citation and a link. Terms .
An episode is a run of days when many cities close to each other (four or more within 350 km on a day, 8 or more in all) each had a daily PM2.5 mean of at least 25 µg/m³ and at least 2 times their usual for that time of year. Found in our own measurements, not picked by hand. How we find episodes . Values are each city's daily mean of its own monitors; causes are the usual kinds for a pattern like this, not a confirmed source.
