SmogRank / Episodes / Thailand

Northern Thailand and Laos, May 2024

For 1 day, on 17 May 2024, 8 cities in Thailand and Laos had PM2.5 at least twice their usual for the time of year. The worst reading was Chiang Rai, Chiang Rai, Thailand: 32.1 µg/m³ on 17 May, about 2.1× its usual 15.4. Ended 17 May.

No cause namedWe have no fire or smoke records for these days, so we only say what the measurements show.
Cities reached8in 2 countries
Days117 May 2024
Worst day17 May8 cities counted
Furthest above usual2.9×Surin

Day by day

17 May 8 cities at twice their usual or more
Nong Bua LamphuLoeiUdon ThaniTha BoKhon KaenVientianeChaiyaphumKalasinPhichitRoi EtUttaraditSakon NakhonNakhon RatchasimaNanPhraeBuri RamNakhon SawanYasothonKamphaeng PhetLop BuriMukdahanChai NatSing BuriSaraburiAmnat CharoenLampangBan Thai TanPhayaoSi Maha PhotSuphan BuriUbon RatchathaniKhlong LuangNong ChokLamphunSai MaiKhlong Sam WaLak SiKhan Na YaoMae SotChiang MaiMueang NonthaburiSaphan SungBan HouakhouaBang KapiChiang KhongBangkokNakhon PathomKanchanaburiPhetchabunNakhon NayokChiang RaiPakxanBueng KanSi Sa KetSukhothaiSurin
14 May151617181920
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

Chiang RaiChiang Rai, 14 May: 19.5 µg/m³Chiang Rai, 15 May: 23.1 µg/m³Chiang Rai, 16 May: 21.4 µg/m³Chiang Rai, 17 May: 32.1 µg/m³, 2.1× its usual 15.4Chiang Rai, 18 May: 20.4 µg/m³Chiang Rai, 19 May: 17.4 µg/m³Chiang Rai, 20 May: 15.5 µg/m³Si Sa KetSi Sa Ket, 14 May: 19.3 µg/m³Si Sa Ket, 15 May: 24.1 µg/m³Si Sa Ket, 16 May: 21.4 µg/m³Si Sa Ket, 17 May: 31.9 µg/m³, 2.2× its usual 14.2Si Sa Ket, 18 May: 12.8 µg/m³Si Sa Ket, 19 May: 11.4 µg/m³Si Sa Ket, 20 May: no readingSukhothaiSukhothai, 14 May: 8.6 µg/m³Sukhothai, 15 May: 11.5 µg/m³Sukhothai, 16 May: 23.8 µg/m³Sukhothai, 17 May: 29.2 µg/m³, 2.3× its usual 12.5Sukhothai, 18 May: 15.2 µg/m³Sukhothai, 19 May: 15.9 µg/m³Sukhothai, 20 May: 11.7 µg/m³SurinSurin, 14 May: 16.6 µg/m³Surin, 15 May: 32.1 µg/m³Surin, 16 May: 23.8 µg/m³Surin, 17 May: 28.8 µg/m³, 2.9× its usual 10.1Surin, 18 May: 16.6 µg/m³Surin, 19 May: 9.5 µg/m³Surin, 20 May: 9.1 µg/m³Bueng KanBueng Kan, 14 May: 19.2 µg/m³Bueng Kan, 15 May: 18.2 µg/m³Bueng Kan, 16 May: 25.4 µg/m³Bueng Kan, 17 May: 28.2 µg/m³, 2.2× its usual 12.9Bueng Kan, 18 May: 24.8 µg/m³Bueng Kan, 19 May: 20.0 µg/m³Bueng Kan, 20 May: 16.7 µg/m³PakxanPakxan, 14 May: 19.2 µg/m³Pakxan, 15 May: 18.2 µg/m³Pakxan, 16 May: 25.4 µg/m³Pakxan, 17 May: 28.2 µg/m³, 2.2× its usual 12.9Pakxan, 18 May: 24.8 µg/m³Pakxan, 19 May: 20.0 µg/m³Pakxan, 20 May: 16.7 µg/m³PhetchabunPhetchabun, 14 May: 12.8 µg/m³Phetchabun, 15 May: 16.0 µg/m³Phetchabun, 16 May: 16.4 µg/m³Phetchabun, 17 May: 26.3 µg/m³, 2.0× its usual 13.0Phetchabun, 18 May: 18.2 µg/m³Phetchabun, 19 May: 19.6 µg/m³Phetchabun, 20 May: 14.6 µg/m³Nakhon NayokNakhon Nayok, 14 May: 19.1 µg/m³Nakhon Nayok, 15 May: 17.7 µg/m³Nakhon Nayok, 16 May: 22.9 µg/m³Nakhon Nayok, 17 May: 25.6 µg/m³, 2.1× its usual 12.0Nakhon Nayok, 18 May: 18.4 µg/m³Nakhon Nayok, 19 May: 16.9 µg/m³Nakhon Nayok, 20 May: 14.8 µg/m³14 May151617181920
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.
Good0–50
Moderate51–100
Sensitive groups101–150
Unhealthy151–200
Very unhealthy201–300
Hazardous301+

Every city it reached

CityDaysHighestUsualAbove usual
SurinSurin, Thailand1 28.817 May10.12.9×
SukhothaiSukhothai, Thailand1 29.217 May12.52.3×
Si Sa KetSi Sa Ket, Thailand1 31.917 May14.22.2×
Bueng KanBueng Kan, Thailand1 28.217 May12.92.2×
PakxanBolikhamsai, Laos1 28.217 May12.92.2×
Chiang RaiChiang Rai, Thailand1 32.117 May15.42.1×
Nakhon NayokNakhon Nayok, Thailand1 25.617 May12.02.1×
PhetchabunPhetchabun, Thailand1 26.317 May13.02.0×

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 24 of 24 episodes in Thailand and Laos since our records began, by cities reached.

Bars: cities reached; colour: the level of the episode's highest daily reading. All 24.

Use this page

SmogRank, Northern Thailand and Laos, May 2024: 8 cities with PM2.5 at twice their usual or more, 17 May 2024, smogrank.com/episodes/2024-05-northern-thailand-and-laos (accessed 5 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.