SmogRank / Episodes / Thailand
North-western Thailand, May 2023
For 3 days, from 16 to 18 May 2023, 30 cities in Thailand and Laos had PM2.5 at least twice their usual for the time of year. The worst reading was Ubon Ratchathani, Ubon Ratchathani, Thailand: 51.2 µg/m³ on 18 May, about 2.7× its usual 18.9.
No cause named We have no fire or smoke records for these days, so we only say what the measurements show.
Cities reached 30 in 2 countries
Days 3 16 to 18 May 2023
Worst day 17 May 21 cities counted
Furthest above usual 2.8× Pakxan
Day by day
Play 17 May 21 cities at twice their usual or more
Khon Kaen Roi Et Sing Buri Nakhon Sawan Khlong Luang Nong Chok Khlong Sam Wa Khan Na Yao Lat Krabang Lak Si Bueng Kum Saphan Sung Tha Bo Bang Kapi Ban Khlong Prawet Bang Bo District Bang Na Bangkok Vientiane Phra Pradaeng Bang Khun Thian Mukdahan Ban Talat Bueng Sukhothai Chanthaburi Ban Chang Kanchanaburi Ratchaburi Trat Tak Tha Yang Nan Hua Hin Mae Sot Lampang Lamphun Chiang Mai Sai Mai Ban Samae Dam Chai Nat Uttaradit Laem Chabang Sakon Nakhon Saraburi Nakhon Pathom Mueang Nonthaburi Samut Sakhon Phichit Phrae Udon Thani Kamphaeng Phet Lop Buri Rayong Si Maha Phot Nong Khaem Samut Prakan Chaiyaphum Nakhon Ratchasima Phra Nakhon Si Ayutthaya Suphan Buri Loei Phetchabun Si Sa Ket Aranyaprathet Buri Ram Ubon Ratchathani Pakxan 13 May 14 15 16 17 18 19 20 21 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 Khaem Nong Khaem, 13 May: 14.3 µg/m³, 0.8× usual Nong Khaem, 14 May: 16.4 µg/m³, 0.9× usual Nong Khaem, 15 May: 31.7 µg/m³, 1.8× usual Nong Khaem, 16 May: 37.3 µg/m³, 2.2× usual Nong Khaem, 17 May: 35.1 µg/m³, 2.0× usual Nong Khaem, 18 May: 32.5 µg/m³, 1.9× usual Nong Khaem, 19 May: 29.5 µg/m³, 1.7× usual Nong Khaem, 20 May: 31.0 µg/m³, 1.8× usual Nong Khaem, 21 May: 32.2 µg/m³, 1.9× usual Samut Sakhon Samut Sakhon, 13 May: 9.4 µg/m³, 0.5× usual Samut Sakhon, 14 May: 11.8 µg/m³, 0.7× usual Samut Sakhon, 15 May: 23.7 µg/m³, 1.4× usual Samut Sakhon, 16 May: 36.2 µg/m³, 2.1× usual Samut Sakhon, 17 May: 27.1 µg/m³, 1.6× usual Samut Sakhon, 18 May: 23.9 µg/m³, 1.4× usual Samut Sakhon, 19 May: 21.6 µg/m³, 1.3× usual Samut Sakhon, 20 May: 23.5 µg/m³, 1.4× usual Samut Sakhon, 21 May: 23.3 µg/m³, 1.4× usual Nakhon Pathom Nakhon Pathom, 13 May: 13.3 µg/m³, 0.9× usual Nakhon Pathom, 14 May: 16.5 µg/m³, 1.1× usual Nakhon Pathom, 15 May: 27.6 µg/m³, 1.9× usual Nakhon Pathom, 16 May: 30.3 µg/m³, 2.1× usual Nakhon Pathom, 17 May: 29.2 µg/m³, 2.0× usual Nakhon Pathom, 18 May: 24.0 µg/m³, 1.7× usual Nakhon Pathom, 19 May: 23.5 µg/m³, 1.6× usual Nakhon Pathom, 20 May: 23.2 µg/m³, 1.6× usual Nakhon Pathom, 21 May: 26.5 µg/m³, 1.8× usual Mueang Nonthaburi Mueang Nonthaburi, 13 May: 12.6 µg/m³, 0.9× usual Mueang Nonthaburi, 14 May: 13.6 µg/m³, 1.0× usual Mueang Nonthaburi, 15 May: 25.9 µg/m³, 1.9× usual Mueang Nonthaburi, 16 May: 28.9 µg/m³, 2.1× usual Mueang Nonthaburi, 17 May: 27.7 µg/m³, 2.0× usual Mueang Nonthaburi, 18 May: 25.0 µg/m³, 1.8× usual Mueang Nonthaburi, 19 May: 25.4 µg/m³, 1.9× usual Mueang Nonthaburi, 20 May: 25.5 µg/m³, 1.9× usual Mueang Nonthaburi, 21 May: 27.0 µg/m³, 2.0× usual Samut Prakan Samut Prakan, 13 May: 13.0 µg/m³, 1.0× usual Samut Prakan, 14 May: 11.8 µg/m³, 0.9× usual Samut Prakan, 15 May: 24.2 µg/m³, 1.9× usual Samut Prakan, 16 May: 28.4 µg/m³, 2.2× usual Samut Prakan, 17 May: 28.6 µg/m³, 2.2× usual Samut Prakan, 18 May: 27.4 µg/m³, 2.1× usual Samut Prakan, 19 May: 26.5 µg/m³, 2.1× usual Samut Prakan, 20 May: no reading Samut Prakan, 21 May: no reading Ubon Ratchathani Ubon Ratchathani, 13 May: no reading Ubon Ratchathani, 14 May: no reading Ubon Ratchathani, 15 May: no reading Ubon Ratchathani, 16 May: no reading Ubon Ratchathani, 17 May: 47.9 µg/m³, 2.5× usual Ubon Ratchathani, 18 May: 51.2 µg/m³, 2.7× usual Ubon Ratchathani, 19 May: no reading Ubon Ratchathani, 20 May: 55.8 µg/m³, 3.0× usual Ubon Ratchathani, 21 May: 49.0 µg/m³, 2.6× usual Si Maha Phot Si Maha Phot, 13 May: no reading Si Maha Phot, 14 May: no reading Si Maha Phot, 15 May: no reading Si Maha Phot, 16 May: no reading Si Maha Phot, 17 May: 40.6 µg/m³, 2.2× usual Si Maha Phot, 18 May: 36.9 µg/m³, 2.0× usual Si Maha Phot, 19 May: no reading Si Maha Phot, 20 May: 39.2 µg/m³, 2.1× usual Si Maha Phot, 21 May: 36.7 µg/m³, 2.0× usual Nakhon Ratchasima Nakhon Ratchasima, 13 May: no reading Nakhon Ratchasima, 14 May: no reading Nakhon Ratchasima, 15 May: no reading Nakhon Ratchasima, 16 May: no reading Nakhon Ratchasima, 17 May: 39.9 µg/m³, 2.3× usual Nakhon Ratchasima, 18 May: 35.5 µg/m³, 2.0× usual Nakhon Ratchasima, 19 May: no reading Nakhon Ratchasima, 20 May: 40.0 µg/m³, 2.3× usual Nakhon Ratchasima, 21 May: 37.7 µg/m³, 2.2× usual Ban Samae Dam Ban Samae Dam, 13 May: no reading Ban Samae Dam, 14 May: no reading Ban Samae Dam, 15 May: no reading Ban Samae Dam, 16 May: no reading Ban Samae Dam, 17 May: 35.3 µg/m³, 2.0× usual Ban Samae Dam, 18 May: 32.0 µg/m³, 1.8× usual Ban Samae Dam, 19 May: no reading Ban Samae Dam, 20 May: no reading Ban Samae Dam, 21 May: no reading Suphan Buri Suphan Buri, 13 May: no reading Suphan Buri, 14 May: no reading Suphan Buri, 15 May: no reading Suphan Buri, 16 May: no reading Suphan Buri, 17 May: 34.9 µg/m³, 2.5× usual Suphan Buri, 18 May: 29.5 µg/m³, 2.1× usual Suphan Buri, 19 May: no reading Suphan Buri, 20 May: 26.6 µg/m³, 1.9× usual Suphan Buri, 21 May: 29.1 µg/m³, 2.1× usual Si Sa Ket Si Sa Ket, 13 May: no reading Si Sa Ket, 14 May: no reading Si Sa Ket, 15 May: no reading Si Sa Ket, 16 May: no reading Si Sa Ket, 17 May: 34.6 µg/m³, 2.5× usual Si Sa Ket, 18 May: 35.7 µg/m³, 2.6× usual Si Sa Ket, 19 May: no reading Si Sa Ket, 20 May: 38.5 µg/m³, 2.8× usual Si Sa Ket, 21 May: 36.5 µg/m³, 2.7× usual Lop Buri Lop Buri, 13 May: no reading Lop Buri, 14 May: no reading Lop Buri, 15 May: no reading Lop Buri, 16 May: no reading Lop Buri, 17 May: 34.3 µg/m³, 2.2× usual Lop Buri, 18 May: 33.6 µg/m³, 2.1× usual Lop Buri, 19 May: no reading Lop Buri, 20 May: 36.0 µg/m³, 2.3× usual Lop Buri, 21 May: 36.7 µg/m³, 2.3× usual Buri Ram Buri Ram, 13 May: no reading Buri Ram, 14 May: no reading Buri Ram, 15 May: no reading Buri Ram, 16 May: no reading Buri Ram, 17 May: 34.2 µg/m³, 2.7× usual Buri Ram, 18 May: 32.5 µg/m³, 2.6× usual Buri Ram, 19 May: no reading Buri Ram, 20 May: 35.2 µg/m³, 2.8× usual Buri Ram, 21 May: 33.0 µg/m³, 2.6× usual Saraburi Saraburi, 13 May: no reading Saraburi, 14 May: no reading Saraburi, 15 May: no reading Saraburi, 16 May: no reading Saraburi, 17 May: 33.0 µg/m³, 2.1× usual Saraburi, 18 May: 33.0 µg/m³, 2.1× usual Saraburi, 19 May: no reading Saraburi, 20 May: 34.9 µg/m³, 2.2× usual Saraburi, 21 May: 33.9 µg/m³, 2.2× usual Phra Nakhon Si Ayut… Phra Nakhon Si Ayutthaya, 13 May: no reading Phra Nakhon Si Ayutthaya, 14 May: no reading Phra Nakhon Si Ayutthaya, 15 May: no reading Phra Nakhon Si Ayutthaya, 16 May: no reading Phra Nakhon Si Ayutthaya, 17 May: 32.5 µg/m³, 2.3× usual Phra Nakhon Si Ayutthaya, 18 May: 29.8 µg/m³, 2.1× usual Phra Nakhon Si Ayutthaya, 19 May: no reading Phra Nakhon Si Ayutthaya, 20 May: 31.1 µg/m³, 2.2× usual Phra Nakhon Si Ayutthaya, 21 May: 31.8 µg/m³, 2.3× usual Rayong Rayong, 13 May: no reading Rayong, 14 May: no reading Rayong, 15 May: no reading Rayong, 16 May: no reading Rayong, 17 May: 30.7 µg/m³, 2.2× usual Rayong, 18 May: 26.3 µg/m³, 1.9× usual Rayong, 19 May: no reading Rayong, 20 May: 29.5 µg/m³, 2.1× usual Rayong, 21 May: 27.4 µg/m³, 2.0× usual Chaiyaphum Chaiyaphum, 13 May: no reading Chaiyaphum, 14 May: no reading Chaiyaphum, 15 May: no reading Chaiyaphum, 16 May: no reading Chaiyaphum, 17 May: 30.1 µg/m³, 2.3× usual Chaiyaphum, 18 May: 29.0 µg/m³, 2.2× usual Chaiyaphum, 19 May: no reading Chaiyaphum, 20 May: 35.3 µg/m³, 2.7× usual Chaiyaphum, 21 May: 36.3 µg/m³, 2.8× usual Phetchabun Phetchabun, 13 May: no reading Phetchabun, 14 May: no reading Phetchabun, 15 May: no reading Phetchabun, 16 May: no reading Phetchabun, 17 May: 29.9 µg/m³, 2.3× usual Phetchabun, 18 May: 33.4 µg/m³, 2.6× usual Phetchabun, 19 May: no reading Phetchabun, 20 May: 44.6 µg/m³, 3.5× usual Phetchabun, 21 May: 41.9 µg/m³, 3.2× usual Sakon Nakhon Sakon Nakhon, 13 May: no reading Sakon Nakhon, 14 May: no reading Sakon Nakhon, 15 May: no reading Sakon Nakhon, 16 May: no reading Sakon Nakhon, 17 May: 29.3 µg/m³, 2.1× usual Sakon Nakhon, 18 May: 28.4 µg/m³, 2.1× usual Sakon Nakhon, 19 May: no reading Sakon Nakhon, 20 May: 37.3 µg/m³, 2.7× usual Sakon Nakhon, 21 May: 38.6 µg/m³, 2.8× usual Sai Mai Sai Mai, 13 May: no reading Sai Mai, 14 May: no reading Sai Mai, 15 May: no reading Sai Mai, 16 May: no reading Sai Mai, 17 May: 28.7 µg/m³, 2.0× usual Sai Mai, 18 May: 26.0 µg/m³, 1.8× usual Sai Mai, 19 May: no reading Sai Mai, 20 May: 25.2 µg/m³, 1.8× usual Sai Mai, 21 May: 26.0 µg/m³, 1.8× usual Aranyaprathet Aranyaprathet, 13 May: no reading Aranyaprathet, 14 May: no reading Aranyaprathet, 15 May: no reading Aranyaprathet, 16 May: no reading Aranyaprathet, 17 May: 27.9 µg/m³, 2.7× usual Aranyaprathet, 18 May: 24.1 µg/m³, 2.4× usual Aranyaprathet, 19 May: no reading Aranyaprathet, 20 May: 26.8 µg/m³, 2.6× usual Aranyaprathet, 21 May: 25.8 µg/m³, 2.5× usual Laem Chabang Laem Chabang, 13 May: no reading Laem Chabang, 14 May: no reading Laem Chabang, 15 May: no reading Laem Chabang, 16 May: no reading Laem Chabang, 17 May: 27.9 µg/m³, 2.1× usual Laem Chabang, 18 May: 23.7 µg/m³, 1.7× usual Laem Chabang, 19 May: no reading Laem Chabang, 20 May: 25.9 µg/m³, 1.9× usual Laem Chabang, 21 May: 25.4 µg/m³, 1.9× usual Pakxan Pakxan, 13 May: no reading Pakxan, 14 May: no reading Pakxan, 15 May: no reading Pakxan, 16 May: no reading Pakxan, 17 May: 24.2 µg/m³, 1.8× usual Pakxan, 18 May: 36.7 µg/m³, 2.8× usual Pakxan, 19 May: no reading Pakxan, 20 May: 53.5 µg/m³, 4.0× usual Pakxan, 21 May: 48.9 µg/m³, 3.7× usual Loei Loei, 13 May: no reading Loei, 14 May: no reading Loei, 15 May: no reading Loei, 16 May: no reading Loei, 17 May: 24.4 µg/m³, 1.9× usual Loei, 18 May: 33.3 µg/m³, 2.6× usual Loei, 19 May: no reading Loei, 20 May: 31.2 µg/m³, 2.4× usual Loei, 21 May: 34.2 µg/m³, 2.7× usual Uttaradit Uttaradit, 13 May: no reading Uttaradit, 14 May: no reading Uttaradit, 15 May: no reading Uttaradit, 16 May: no reading Uttaradit, 17 May: 27.0 µg/m³, 1.7× usual Uttaradit, 18 May: 33.0 µg/m³, 2.1× usual Uttaradit, 19 May: no reading Uttaradit, 20 May: 37.7 µg/m³, 2.4× usual Uttaradit, 21 May: 41.9 µg/m³, 2.6× usual Udon Thani Udon Thani, 13 May: no reading Udon Thani, 14 May: no reading Udon Thani, 15 May: no reading Udon Thani, 16 May: no reading Udon Thani, 17 May: 28.5 µg/m³, 1.9× usual Udon Thani, 18 May: 32.5 µg/m³, 2.2× usual Udon Thani, 19 May: no reading Udon Thani, 20 May: 39.2 µg/m³, 2.7× usual Udon Thani, 21 May: 41.0 µg/m³, 2.8× usual Phrae Phrae, 13 May: no reading Phrae, 14 May: no reading Phrae, 15 May: no reading Phrae, 16 May: no reading Phrae, 17 May: 26.4 µg/m³, 1.8× usual Phrae, 18 May: 32.2 µg/m³, 2.2× usual Phrae, 19 May: no reading Phrae, 20 May: 36.9 µg/m³, 2.5× usual Phrae, 21 May: 38.0 µg/m³, 2.6× usual Chai Nat Chai Nat, 13 May: no reading Chai Nat, 14 May: no reading Chai Nat, 15 May: no reading Chai Nat, 16 May: no reading Chai Nat, 17 May: 25.9 µg/m³, 1.7× usual Chai Nat, 18 May: 31.5 µg/m³, 2.1× usual Chai Nat, 19 May: no reading Chai Nat, 20 May: 33.8 µg/m³, 2.2× usual Chai Nat, 21 May: 29.0 µg/m³, 1.9× usual Phichit Phichit, 13 May: no reading Phichit, 14 May: no reading Phichit, 15 May: no reading Phichit, 16 May: no reading Phichit, 17 May: 20.9 µg/m³, 1.8× usual Phichit, 18 May: 26.3 µg/m³, 2.2× usual Phichit, 19 May: no reading Phichit, 20 May: 30.7 µg/m³, 2.6× usual Phichit, 21 May: 32.6 µg/m³, 2.8× usual Kamphaeng Phet Kamphaeng Phet, 13 May: no reading Kamphaeng Phet, 14 May: no reading Kamphaeng Phet, 15 May: no reading Kamphaeng Phet, 16 May: no reading Kamphaeng Phet, 17 May: 23.0 µg/m³, 2.0× usual Kamphaeng Phet, 18 May: 26.2 µg/m³, 2.2× usual Kamphaeng Phet, 19 May: no reading Kamphaeng Phet, 20 May: 27.5 µg/m³, 2.4× usual Kamphaeng Phet, 21 May: 26.7 µg/m³, 2.3× usual 13 May 14 15 16 17 18 19 20 21 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
Pakxan Bolikhamsai, Laos 1 20 May 13.3 4.0× Phetchabun Phetchabun, Thailand 2 20 May 12.9 3.5× Ubon Ratchathani Ubon Ratchathani, Thailand 2 20 May 18.9 3.0× Sakon Nakhon Sakon Nakhon, Thailand 2 21 May 13.7 2.8× Buri Ram Buriram, Thailand 2 20 May 12.5 2.8× Chaiyaphum Chaiyaphum, Thailand 2 21 May 12.9 2.8× Si Sa Ket Si Sa Ket, Thailand 2 20 May 13.7 2.8× Udon Thani Udon Thani, Thailand 1 21 May 14.7 2.8× Phichit Phichit, Thailand 1 21 May 11.7 2.8× Aranyaprathet Sa Kaeo, Thailand 1 17 May 10.2 2.7× Loei Loei, Thailand 1 21 May 12.9 2.7× Uttaradit Uttaradit, Thailand 1 21 May 16.0 2.6× Phrae Phrae, Thailand 1 21 May 14.6 2.6× Suphan Buri Suphan Buri, Thailand 2 17 May 13.9 2.5× Kamphaeng Phet Kamphaeng Phet, Thailand 1 20 May 11.7 2.4× Phra Nakhon Si Ayutthaya Phra Nakhon Si Ayutthaya, Thailand 2 17 May 13.9 2.3× Lop Buri Lopburi, Thailand 2 21 May 15.8 2.3× Nakhon Ratchasima Nakhon Ratchasima, Thailand 2 20 May 17.5 2.3× Samut Prakan Samut Prakan, Thailand 3 17 May 12.8 2.2× Rayong Rayong, Thailand 1 17 May 13.8 2.2× Chai Nat Chai Nat, Thailand 1 20 May 15.2 2.2× Saraburi Saraburi, Thailand 2 20 May 15.7 2.2× Si Maha Phot Prachin Buri, Thailand 2 17 May 18.5 2.2× Nong Khaem Bangkok, Thailand 2 16 May 17.3 2.2× Samut Sakhon Samut Sakhon, Thailand 1 16 May 17.1 2.1× Mueang Nonthaburi Nonthaburi, Thailand 2 16 May 13.7 2.1× Nakhon Pathom Nakhon Pathom, Thailand 2 16 May 14.4 2.1× Laem Chabang Chon Buri, Thailand 1 17 May 13.6 2.1× Ban Samae Dam Bangkok, Thailand 1 17 May 17.4 2.0× Sai Mai Bangkok, Thailand 1 17 May 14.2 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 8 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, North-western Thailand, May 2023: 30 cities with PM2.5 at twice their usual or more, 16 to 18 May 2023, smogrank.com/episodes/2023-05-north-western-thailand-2 (accessed 3 October 2026).
Copy citation Download top 10 (PNG)
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.
