SmogRank / Episodes / Thailand
Northern Thailand and Laos, 16 to 18 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 Laem Chabang Mueang Nonthaburi Sakon Nakhon Nakhon Pathom Chai Nat Uttaradit Saraburi Samut Sakhon Kamphaeng Phet Phichit Samut Prakan Rayong Phrae Udon Thani Lop Buri Nong Khaem Si Maha Phot Chaiyaphum Phra Nakhon Si Ayutthaya Nakhon Ratchasima 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 Nong Khaem, 14 May: 16.4 µg/m³ Nong Khaem, 15 May: 31.7 µg/m³ Nong Khaem, 16 May: 37.3 µg/m³, 2.2× its usual 17.3 Nong Khaem, 17 May: 35.1 µg/m³, 2.0× its usual 17.5 Nong Khaem, 18 May: 32.5 µg/m³ Nong Khaem, 19 May: 29.5 µg/m³ Nong Khaem, 20 May: 31.0 µg/m³ Nong Khaem, 21 May: 32.2 µg/m³ Samut Sakhon Samut Sakhon, 13 May: 9.4 µg/m³ Samut Sakhon, 14 May: 11.8 µg/m³ Samut Sakhon, 15 May: 23.7 µg/m³ Samut Sakhon, 16 May: 36.2 µg/m³, 2.1× its usual 17.1 Samut Sakhon, 17 May: 27.1 µg/m³ Samut Sakhon, 18 May: 23.9 µg/m³ Samut Sakhon, 19 May: 21.6 µg/m³ Samut Sakhon, 20 May: 23.5 µg/m³ Samut Sakhon, 21 May: 23.3 µg/m³ Nakhon Pathom Nakhon Pathom, 13 May: 13.3 µg/m³ Nakhon Pathom, 14 May: 16.5 µg/m³ Nakhon Pathom, 15 May: 27.6 µg/m³ Nakhon Pathom, 16 May: 30.3 µg/m³, 2.1× its usual 14.4 Nakhon Pathom, 17 May: 29.2 µg/m³, 2.1× its usual 14.2 Nakhon Pathom, 18 May: 24.0 µg/m³ Nakhon Pathom, 19 May: 23.5 µg/m³ Nakhon Pathom, 20 May: 23.2 µg/m³ Nakhon Pathom, 21 May: 26.5 µg/m³ Mueang Nonthaburi Mueang Nonthaburi, 13 May: 12.6 µg/m³ Mueang Nonthaburi, 14 May: 13.6 µg/m³ Mueang Nonthaburi, 15 May: 25.9 µg/m³ Mueang Nonthaburi, 16 May: 28.9 µg/m³, 2.1× its usual 13.7 Mueang Nonthaburi, 17 May: 27.7 µg/m³, 2.0× its usual 13.6 Mueang Nonthaburi, 18 May: 25.0 µg/m³ Mueang Nonthaburi, 19 May: 25.4 µg/m³ Mueang Nonthaburi, 20 May: 25.5 µg/m³ Mueang Nonthaburi, 21 May: 27.0 µg/m³ Samut Prakan Samut Prakan, 13 May: 13.0 µg/m³ Samut Prakan, 14 May: 11.8 µg/m³ Samut Prakan, 15 May: 24.2 µg/m³ Samut Prakan, 16 May: 28.4 µg/m³, 2.2× its usual 12.8 Samut Prakan, 17 May: 28.6 µg/m³, 2.2× its usual 12.8 Samut Prakan, 18 May: 27.4 µg/m³, 2.1× its usual 12.8 Samut Prakan, 19 May: 26.5 µg/m³ 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, 2.3× its usual 20.4 Ubon Ratchathani, 18 May: 51.2 µg/m³, 2.7× its usual 18.9 Ubon Ratchathani, 19 May: no reading Ubon Ratchathani, 20 May: 55.8 µg/m³ Ubon Ratchathani, 21 May: 49.0 µg/m³ 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× its usual 18.5 Si Maha Phot, 18 May: 36.9 µg/m³, 2.0× its usual 18.3 Si Maha Phot, 19 May: no reading Si Maha Phot, 20 May: 39.2 µg/m³ Si Maha Phot, 21 May: 36.7 µg/m³ 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× its usual 17.5 Nakhon Ratchasima, 18 May: 35.5 µg/m³, 2.1× its usual 17.3 Nakhon Ratchasima, 19 May: no reading Nakhon Ratchasima, 20 May: 40.0 µg/m³ Nakhon Ratchasima, 21 May: 37.7 µg/m³ 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× its usual 17.4 Ban Samae Dam, 18 May: 32.0 µg/m³ 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× its usual 13.9 Suphan Buri, 18 May: 29.5 µg/m³, 2.1× its usual 13.8 Suphan Buri, 19 May: no reading Suphan Buri, 20 May: 26.6 µg/m³ Suphan Buri, 21 May: 29.1 µg/m³ 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× its usual 13.8 Si Sa Ket, 18 May: 35.7 µg/m³, 2.6× its usual 13.7 Si Sa Ket, 19 May: no reading Si Sa Ket, 20 May: 38.5 µg/m³ Si Sa Ket, 21 May: 36.5 µg/m³ 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× its usual 15.8 Lop Buri, 18 May: 33.6 µg/m³, 2.2× its usual 15.5 Lop Buri, 19 May: no reading Lop Buri, 20 May: 36.0 µg/m³ Lop Buri, 21 May: 36.7 µg/m³ 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× its usual 12.5 Buri Ram, 18 May: 32.5 µg/m³, 2.7× its usual 12.1 Buri Ram, 19 May: no reading Buri Ram, 20 May: 35.2 µg/m³ Buri Ram, 21 May: 33.0 µg/m³ 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× its usual 15.7 Saraburi, 18 May: 33.0 µg/m³, 2.2× its usual 15.3 Saraburi, 19 May: no reading Saraburi, 20 May: 34.9 µg/m³ Saraburi, 21 May: 33.9 µg/m³ 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× its usual 13.9 Phra Nakhon Si Ayutthaya, 18 May: 29.8 µg/m³, 2.2× its usual 13.8 Phra Nakhon Si Ayutthaya, 19 May: no reading Phra Nakhon Si Ayutthaya, 20 May: 31.1 µg/m³ Phra Nakhon Si Ayutthaya, 21 May: 31.8 µg/m³ 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× its usual 13.8 Rayong, 18 May: 26.3 µg/m³ Rayong, 19 May: no reading Rayong, 20 May: 29.5 µg/m³ Rayong, 21 May: 27.4 µg/m³ 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× its usual 12.9 Chaiyaphum, 18 May: 29.0 µg/m³, 2.4× its usual 12.2 Chaiyaphum, 19 May: no reading Chaiyaphum, 20 May: 35.3 µg/m³ Chaiyaphum, 21 May: 36.3 µg/m³ 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× its usual 13.0 Phetchabun, 18 May: 33.4 µg/m³, 2.6× its usual 12.9 Phetchabun, 19 May: no reading Phetchabun, 20 May: 44.6 µg/m³ Phetchabun, 21 May: 41.9 µg/m³ 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× its usual 13.7 Sakon Nakhon, 18 May: 28.4 µg/m³, 2.1× its usual 13.3 Sakon Nakhon, 19 May: no reading Sakon Nakhon, 20 May: 37.3 µg/m³ Sakon Nakhon, 21 May: 38.6 µg/m³ 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× its usual 14.2 Sai Mai, 18 May: 26.0 µg/m³ Sai Mai, 19 May: no reading Sai Mai, 20 May: 25.2 µg/m³ Sai Mai, 21 May: 26.0 µg/m³ 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× its usual 10.2 Aranyaprathet, 18 May: 24.1 µg/m³ Aranyaprathet, 19 May: no reading Aranyaprathet, 20 May: 26.8 µg/m³ Aranyaprathet, 21 May: 25.8 µg/m³ 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× its usual 13.6 Laem Chabang, 18 May: 23.7 µg/m³ Laem Chabang, 19 May: no reading Laem Chabang, 20 May: 25.9 µg/m³ Laem Chabang, 21 May: 25.4 µg/m³ 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 Pakxan, 18 May: 36.7 µg/m³, 2.8× its usual 13.3 Pakxan, 19 May: no reading Pakxan, 20 May: 53.5 µg/m³ Pakxan, 21 May: 48.9 µg/m³ 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 Loei, 18 May: 33.3 µg/m³, 2.6× its usual 12.9 Loei, 19 May: no reading Loei, 20 May: 31.2 µg/m³ Loei, 21 May: 34.2 µg/m³ 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 Uttaradit, 18 May: 33.0 µg/m³, 2.1× its usual 16.0 Uttaradit, 19 May: no reading Uttaradit, 20 May: 37.7 µg/m³ Uttaradit, 21 May: 41.9 µg/m³ 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 Udon Thani, 18 May: 32.5 µg/m³, 2.2× its usual 14.7 Udon Thani, 19 May: no reading Udon Thani, 20 May: 39.2 µg/m³ Udon Thani, 21 May: 41.0 µg/m³ 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 Phrae, 18 May: 32.2 µg/m³, 2.2× its usual 14.6 Phrae, 19 May: no reading Phrae, 20 May: 36.9 µg/m³ Phrae, 21 May: 38.0 µg/m³ 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 Chai Nat, 18 May: 31.5 µg/m³, 2.1× its usual 15.2 Chai Nat, 19 May: no reading Chai Nat, 20 May: 33.8 µg/m³ Chai Nat, 21 May: 29.0 µg/m³ 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 Phichit, 18 May: 26.3 µg/m³, 2.2× its usual 11.7 Phichit, 19 May: no reading Phichit, 20 May: 30.7 µg/m³ Phichit, 21 May: 32.6 µg/m³ 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 Kamphaeng Phet, 18 May: 26.2 µg/m³, 2.2× its usual 11.7 Kamphaeng Phet, 19 May: no reading Kamphaeng Phet, 20 May: 27.5 µg/m³ Kamphaeng Phet, 21 May: 26.7 µg/m³ 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 18 May 13.3 2.8× Ubon Ratchathani Ubon Ratchathani, Thailand 2 18 May 18.9 2.7× Buri Ram Buriram, Thailand 2 17 May 12.5 2.7× Aranyaprathet Sa Kaeo, Thailand 1 17 May 10.2 2.7× Si Sa Ket Si Sa Ket, Thailand 2 18 May 13.7 2.6× Phetchabun Phetchabun, Thailand 2 18 May 12.9 2.6× Loei Loei, Thailand 1 18 May 12.9 2.6× Suphan Buri Suphan Buri, Thailand 2 17 May 13.9 2.5× Nakhon Ratchasima Nakhon Ratchasima, Thailand 2 17 May 17.5 2.3× Phra Nakhon Si Ayutthaya Phra Nakhon Si Ayutthaya, Thailand 2 17 May 13.9 2.3× Chaiyaphum Chaiyaphum, Thailand 2 17 May 12.9 2.3× Si Maha Phot Prachin Buri, Thailand 2 17 May 18.5 2.2× Nong Khaem Bangkok, Thailand 2 16 May 17.3 2.2× Lop Buri Lopburi, Thailand 2 17 May 15.8 2.2× Udon Thani Udon Thani, Thailand 1 18 May 14.7 2.2× Phrae Phrae, Thailand 1 18 May 14.6 2.2× Rayong Rayong, Thailand 1 17 May 13.8 2.2× Samut Prakan Samut Prakan, Thailand 3 17 May 12.8 2.2× Phichit Phichit, Thailand 1 18 May 11.7 2.2× Kamphaeng Phet Kamphaeng Phet, Thailand 1 18 May 11.7 2.2× Samut Sakhon Samut Sakhon, Thailand 1 16 May 17.1 2.1× Saraburi Saraburi, Thailand 2 17 May 15.7 2.1× Uttaradit Uttaradit, Thailand 1 18 May 16.0 2.1× Chai Nat Chai Nat, Thailand 1 18 May 15.2 2.1× Nakhon Pathom Nakhon Pathom, Thailand 2 16 May 14.4 2.1× Sakon Nakhon Sakon Nakhon, Thailand 2 17 May 13.7 2.1× Mueang Nonthaburi Nonthaburi, Thailand 2 16 May 13.7 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, 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 8 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, Northern Thailand and Laos, 16 to 18 May 2023: 30 cities with PM2.5 at twice their usual or more, 16 to 18 May 2023, smogrank.com/episodes/2023-05-16-northern-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.
