SmogRank / Episodes / Thailand
Western 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 Sai Mai Lak Si Lat Krabang Bang Bo District Nong Chok Phrae Uttaradit Saphan Sung Vientiane Nakhon Pathom Nong Khaem Phra Nakhon Si Ayutthaya Phra Pradaeng Roi Et Bangkok Rayong Si Sa Ket Chiang Rai Lampang Buri Ram Samut Sakhon Hua Hin Sukhothai Ban Houakhoua Bang Na Ban Khlong Prawet Ban Samae Dam Mukdahan Pakxan Tha Bo Loei 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, 0.7× usual Nong Bua Lamphu, 29 January: 34.2 µg/m³, 1.2× usual Nong Bua Lamphu, 30 January: 53.5 µg/m³, 1.9× usual Nong Bua Lamphu, 31 January: 81.1 µg/m³, 2.8× usual Nong Bua Lamphu, 1 February: 76.5 µg/m³, 2.7× usual 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, 0.6× usual Loei, 29 January: 45.0 µg/m³, 1.3× usual Loei, 30 January: 60.7 µg/m³, 1.8× usual Loei, 31 January: 77.4 µg/m³, 2.3× usual Loei, 1 February: 88.9 µg/m³, 2.6× usual Loei, 2 February: no reading Loei, 3 February: no reading Loei, 4 February: no reading Sukhothai Sukhothai, 28 January: 53.0 µg/m³, 1.5× usual Sukhothai, 29 January: 55.5 µg/m³, 1.6× usual Sukhothai, 30 January: 67.4 µg/m³, 1.9× usual Sukhothai, 31 January: 72.2 µg/m³, 2.1× usual Sukhothai, 1 February: 81.0 µg/m³, 2.3× usual 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, 0.7× usual Udon Thani, 29 January: 32.3 µg/m³, 1.2× usual Udon Thani, 30 January: 44.2 µg/m³, 1.7× usual Udon Thani, 31 January: 60.7 µg/m³, 2.3× usual Udon Thani, 1 February: 76.3 µg/m³, 2.9× usual 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, 0.8× usual Pakxan, 29 January: 36.3 µg/m³, 1.4× usual Pakxan, 30 January: 41.9 µg/m³, 1.6× usual Pakxan, 31 January: 58.3 µg/m³, 2.3× usual Pakxan, 1 February: 63.8 µg/m³, 2.5× usual 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, 0.9× usual Sakon Nakhon, 29 January: 25.4 µg/m³, 1.3× usual Sakon Nakhon, 30 January: 32.5 µg/m³, 1.7× usual Sakon Nakhon, 31 January: 44.5 µg/m³, 2.3× usual Sakon Nakhon, 1 February: 62.0 µg/m³, 3.2× usual 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, 0.8× usual Tha Bo, 29 January: 50.2 µg/m³, 1.1× usual Tha Bo, 30 January: 90.5 µg/m³, 1.9× usual Tha Bo, 31 January: 92.7 µg/m³, 2.0× usual Tha Bo, 1 February: 122.0 µg/m³, 2.6× usual 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, 0.6× usual Vientiane, 29 January: 50.2 µg/m³, 0.9× usual Vientiane, 30 January: 90.5 µg/m³, 1.6× usual Vientiane, 31 January: 92.7 µg/m³, 1.6× usual Vientiane, 1 February: 122.0 µg/m³, 2.1× usual 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, 0.9× usual Bang Na, 29 January: 26.7 µg/m³, 0.7× usual Bang Na, 30 January: 36.1 µg/m³, 0.9× usual Bang Na, 31 January: 57.0 µg/m³, 1.4× usual Bang Na, 1 February: 98.5 µg/m³, 2.4× usual 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, 1.6× usual Lampang, 29 January: 60.4 µg/m³, 1.5× usual Lampang, 30 January: 62.9 µg/m³, 1.5× usual Lampang, 31 January: 77.4 µg/m³, 1.9× usual Lampang, 1 February: 88.7 µg/m³, 2.2× usual 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, 0.9× usual Ban Samae Dam, 29 January: 25.4 µg/m³, 0.7× usual Ban Samae Dam, 30 January: 32.7 µg/m³, 0.9× usual Ban Samae Dam, 31 January: 58.9 µg/m³, 1.6× usual Ban Samae Dam, 1 February: 88.5 µg/m³, 2.4× usual 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, 1.0× usual Nong Khaem, 29 January: 30.2 µg/m³, 0.7× usual Nong Khaem, 30 January: 36.7 µg/m³, 0.9× usual Nong Khaem, 31 January: 66.2 µg/m³, 1.6× usual Nong Khaem, 1 February: 85.6 µg/m³, 2.1× usual 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, 1.2× usual Samut Sakhon, 29 January: 30.6 µg/m³, 0.8× usual Samut Sakhon, 30 January: 35.3 µg/m³, 1.0× usual Samut Sakhon, 31 January: 67.2 µg/m³, 1.8× usual Samut Sakhon, 1 February: 83.1 µg/m³, 2.3× usual 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, 0.8× usual Lat Krabang, 29 January: 25.4 µg/m³, 0.6× usual Lat Krabang, 30 January: 40.4 µg/m³, 1.0× usual Lat Krabang, 31 January: 57.0 µg/m³, 1.4× usual Lat Krabang, 1 February: 82.8 µg/m³, 2.0× usual 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, 1.0× usual Nakhon Pathom, 29 January: 30.5 µg/m³, 0.8× usual Nakhon Pathom, 30 January: 33.3 µg/m³, 0.9× usual Nakhon Pathom, 31 January: 60.3 µg/m³, 1.6× usual Nakhon Pathom, 1 February: 80.5 µg/m³, 2.1× usual 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, 0.9× usual Ban Khlong Prawet, 29 January: 21.8 µg/m³, 0.6× usual Ban Khlong Prawet, 30 January: 32.2 µg/m³, 1.0× usual Ban Khlong Prawet, 31 January: 48.5 µg/m³, 1.4× usual Ban Khlong Prawet, 1 February: 79.7 µg/m³, 2.4× usual 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, 0.9× usual Bangkok, 29 January: 26.7 µg/m³, 0.8× usual Bangkok, 30 January: 35.3 µg/m³, 1.0× usual Bangkok, 31 January: 57.9 µg/m³, 1.6× usual Bangkok, 1 February: 78.4 µg/m³, 2.2× usual 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, 0.9× usual Saphan Sung, 29 January: 26.8 µg/m³, 0.7× usual Saphan Sung, 30 January: 37.9 µg/m³, 1.0× usual Saphan Sung, 31 January: 54.6 µg/m³, 1.5× usual Saphan Sung, 1 February: 78.3 µg/m³, 2.1× usual 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, 1.0× usual Lak Si, 29 January: 26.2 µg/m³, 0.7× usual Lak Si, 30 January: 36.5 µg/m³, 1.0× usual Lak Si, 31 January: 59.1 µg/m³, 1.6× usual Lak Si, 1 February: 76.7 µg/m³, 2.0× usual 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, 0.9× usual Phra Nakhon Si Ayutthaya, 29 January: 29.5 µg/m³, 0.8× usual Phra Nakhon Si Ayutthaya, 30 January: 34.5 µg/m³, 1.0× usual Phra Nakhon Si Ayutthaya, 31 January: 51.5 µg/m³, 1.4× usual Phra Nakhon Si Ayutthaya, 1 February: 75.4 µg/m³, 2.1× usual 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, 1.6× usual Phrae, 31 January: 67.5 µg/m³, 1.8× usual Phrae, 1 February: 74.8 µg/m³, 2.0× usual 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, 0.8× usual Nong Chok, 29 January: 20.3 µg/m³, 0.6× usual Nong Chok, 30 January: 38.8 µg/m³, 1.1× usual Nong Chok, 31 January: 55.1 µg/m³, 1.5× usual Nong Chok, 1 February: 73.7 µg/m³, 2.0× usual 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, 0.8× usual Phra Pradaeng, 29 January: 21.6 µg/m³, 0.6× usual Phra Pradaeng, 30 January: 26.6 µg/m³, 0.8× usual Phra Pradaeng, 31 January: 46.5 µg/m³, 1.4× usual Phra Pradaeng, 1 February: 73.3 µg/m³, 2.1× usual 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, 1.2× usual Uttaradit, 29 January: 37.8 µg/m³, 1.0× usual Uttaradit, 30 January: 51.8 µg/m³, 1.4× usual Uttaradit, 31 January: 58.4 µg/m³, 1.6× usual Uttaradit, 1 February: 73.2 µg/m³, 2.0× usual 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, 1.0× usual Sai Mai, 29 January: 22.3 µg/m³, 0.6× usual Sai Mai, 30 January: 36.9 µg/m³, 1.0× usual Sai Mai, 31 January: 55.3 µg/m³, 1.5× usual Sai Mai, 1 February: 72.4 µg/m³, 2.0× usual 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, 0.8× usual Bang Bo District, 30 January: no reading Bang Bo District, 31 January: 45.5 µg/m³, 1.4× usual Bang Bo District, 1 February: 67.3 µg/m³, 2.0× usual 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, 0.7× usual Mukdahan, 29 January: 31.3 µg/m³, 1.2× usual Mukdahan, 30 January: 36.1 µg/m³, 1.3× usual Mukdahan, 31 January: 42.2 µg/m³, 1.6× usual Mukdahan, 1 February: 64.8 µg/m³, 2.4× usual 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, 1.3× usual Ban Houakhoua, 29 January: 26.6 µg/m³, 1.0× usual Ban Houakhoua, 30 January: 38.4 µg/m³, 1.5× usual Ban Houakhoua, 31 January: 44.1 µg/m³, 1.7× usual Ban Houakhoua, 1 February: 63.8 µg/m³, 2.4× usual 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, 1.7× usual Chiang Rai, 29 January: 33.9 µg/m³, 1.2× usual Chiang Rai, 30 January: 37.0 µg/m³, 1.3× usual Chiang Rai, 31 January: 45.7 µg/m³, 1.6× usual Chiang Rai, 1 February: 62.2 µg/m³, 2.2× usual 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, 0.6× usual Buri Ram, 29 January: 25.4 µg/m³, 0.9× usual Buri Ram, 30 January: 33.3 µg/m³, 1.2× usual Buri Ram, 31 January: 50.3 µg/m³, 1.9× usual Buri Ram, 1 February: 61.1 µg/m³, 2.3× usual 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, 1.5× usual Hua Hin, 29 January: 25.8 µg/m³, 1.0× usual Hua Hin, 30 January: 31.7 µg/m³, 1.2× usual Hua Hin, 31 January: 42.8 µg/m³, 1.7× usual Hua Hin, 1 February: 60.4 µg/m³, 2.3× usual 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, 1.2× usual Rayong, 29 January: 18.8 µg/m³, 0.7× usual Rayong, 30 January: 24.9 µg/m³, 0.9× usual Rayong, 31 January: 39.8 µg/m³, 1.4× usual Rayong, 1 February: 59.5 µg/m³, 2.2× usual 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, 0.5× usual Roi Et, 29 January: 23.6 µg/m³, 0.9× usual Roi Et, 30 January: 29.5 µg/m³, 1.1× usual Roi Et, 31 January: 42.3 µg/m³, 1.6× usual Roi Et, 1 February: 55.2 µg/m³, 2.1× usual 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, 0.5× usual Si Sa Ket, 29 January: 19.5 µg/m³, 0.8× usual Si Sa Ket, 30 January: 26.8 µg/m³, 1.1× usual Si Sa Ket, 31 January: 32.7 µg/m³, 1.4× usual Si Sa Ket, 1 February: 52.7 µg/m³, 2.2× usual 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× Loei Loei, Thailand 2 1 February 33.8 2.6× Tha Bo Nong Khai, Thailand 1 1 February 47.0 2.6× Pakxan Bolikhamsai, Laos 2 1 February 25.5 2.5× Bang Na Bangkok, Thailand 1 1 February 40.4 2.4× Ban Houakhoua Bokeo, Laos 1 1 February 26.4 2.4× Ban Samae Dam Bangkok, Thailand 1 1 February 36.7 2.4× Mukdahan Mukdahan, Thailand 1 1 February 27.1 2.4× Ban Khlong Prawet Bangkok, Thailand 1 1 February 33.7 2.4× Hua Hin Prachuap Khiri Khan, Thailand 1 1 February 25.9 2.3× Sukhothai Sukhothai, Thailand 2 1 February 34.9 2.3× Buri Ram Buriram, Thailand 1 1 February 26.8 2.3× Samut Sakhon Samut Sakhon, Thailand 1 1 February 36.7 2.3× Chiang Rai Chiang Rai, Thailand 1 1 February 28.0 2.2× Bangkok Bangkok, Thailand 1 1 February 35.4 2.2× Si Sa Ket Si Sa Ket, Thailand 1 1 February 24.1 2.2× Rayong Rayong, Thailand 1 1 February 27.5 2.2× Lampang Lampang, Thailand 1 1 February 41.2 2.2× Phra Pradaeng Samut Prakan, Thailand 1 1 February 34.3 2.1× Vientiane Vientiane Prefecture, Laos 1 1 February 57.2 2.1× Nakhon Pathom Nakhon Pathom, Thailand 1 1 February 38.0 2.1× Phra Nakhon Si Ayutthaya Phra Nakhon Si Ayutthaya, Thailand 1 1 February 35.7 2.1× Saphan Sung Bangkok, Thailand 1 1 February 37.4 2.1× Roi Et Roi Et, Thailand 1 1 February 26.4 2.1× Nong Khaem Bangkok, Thailand 1 1 February 41.6 2.1× Phrae Phrae, Thailand 1 1 February 36.8 2.0× Nong Chok Bangkok, Thailand 1 1 February 36.4 2.0× Lat Krabang Bangkok, Thailand 1 1 February 40.9 2.0× Lak Si Bangkok, Thailand 1 1 February 38.0 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× Uttaradit Uttaradit, Thailand 1 1 February 36.6 2.0×
Daily means in µg/m³. Usual: the city's median for this time of year (its days within 21 days of the date, every year, leaving out the week around it). Above usual: its highest day against that.
Against other episodes in Thailand and Laos
Number 7 of 24 episodes in Thailand and Laos since our records began, by cities reached.
Central Thailand, March 2025 53 Western Thailand, February 2024 51 Central Thailand, January 2025 50 North-western Thailand, April and May 2024 45 North-western Thailand, May 2023 41 Western Thailand, April 2023 35 Western Thailand and Laos, January and February 2023 34 North-western Thailand, May 2023 30 North-eastern Thailand, October 2024 24 Northern Thailand, November and December 2025 22 Western Thailand, February 2025 17 North-western Thailand, May 2023 17 Bars: cities reached; colour: the level of the episode's highest daily reading. All 24 .
Use this page SmogRank, Western 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-western-thailand-and-laos (accessed 3 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.
