SmogRank / Episodes / Thailand
Northern Thailand and Laos around Bangkok, 5 to 8 April 2023
For 4 days, from 5 to 8 April 2023, 30 cities in Thailand and Laos had PM2.5 at least twice their usual for the time of year. The worst reading was Mae Sai, Chiang Rai, Thailand: 345.0 µg/m³ on 7 April, about 4.5× its usual 76.4. Ended 8 April.
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 4 5 to 8 April 2023
Worst day 7 April 17 cities counted
Furthest above usual 4.5× Mae Sai
Day by day
Play 7 April 17 cities at twice their usual or more
Phetchabun Phichit Chaiyaphum Nakhon Sawan Khon Kaen Uttaradit Nakhon Ratchasima Chai Nat Kamphaeng Phet Lop Buri Sing Buri Saraburi Kalasin Tak Phra Nakhon Si Ayutthaya Buri Ram Suphan Buri Roi Et Khlong Luang Si Maha Phot Sai Mai Nong Chok Khlong Sam Wa Lak Si Khan Na Yao Mae Sot Saphan Sung Bang Kapi Lat Krabang Sakon Nakhon Bang Na Phra Pradaeng Bang Bo District Aranyaprathet Kanchanaburi Si Sa Ket Ratchaburi Mukdahan Laem Chabang Ban Talat Bueng Ubon Ratchathani Ban Chang Rayong Chanthaburi Trat Ban Khlong Prawet Hua Hin Bueng Kum Ban Samae Dam Bangkok Mueang Nonthaburi Ban Thai Tan Udon Thani Samut Prakan Nakhon Pathom Samut Sakhon Nong Khaem Bang Khun Thian Phrae Sukhothai Vientiane Lamphun Pakxan Bueng Kan Lampang Tha Bo Nong Bua Lamphu Nan Phayao Chiang Rai Chiang Mai Ban Houakhoua Chiang Khong Loei Mae Sai 2 Apr 3 4 5 6 7 8 9 10 11 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
Ban Samae Dam Ban Samae Dam, 2 April: 24.9 µg/m³ Ban Samae Dam, 3 April: 31.8 µg/m³ Ban Samae Dam, 4 April: 44.7 µg/m³ Ban Samae Dam, 5 April: 48.7 µg/m³, 2.0× its usual 23.8 Ban Samae Dam, 6 April: no reading Ban Samae Dam, 7 April: 44.4 µg/m³ Ban Samae Dam, 8 April: 23.0 µg/m³ Ban Samae Dam, 9 April: 20.2 µg/m³ Ban Samae Dam, 10 April: 17.4 µg/m³ Ban Samae Dam, 11 April: 27.1 µg/m³ Samut Prakan Samut Prakan, 2 April: no reading Samut Prakan, 3 April: 36.7 µg/m³ Samut Prakan, 4 April: 39.6 µg/m³ Samut Prakan, 5 April: 46.8 µg/m³, 2.3× its usual 20.0 Samut Prakan, 6 April: 43.9 µg/m³, 2.2× its usual 19.8 Samut Prakan, 7 April: 33.1 µg/m³ Samut Prakan, 8 April: 19.3 µg/m³ Samut Prakan, 9 April: no reading Samut Prakan, 10 April: no reading Samut Prakan, 11 April: 19.4 µg/m³ Bueng Kum Bueng Kum, 2 April: 20.8 µg/m³ Bueng Kum, 3 April: 25.6 µg/m³ Bueng Kum, 4 April: 35.9 µg/m³ Bueng Kum, 5 April: 44.5 µg/m³, 2.0× its usual 22.0 Bueng Kum, 6 April: no reading Bueng Kum, 7 April: 36.3 µg/m³ Bueng Kum, 8 April: 25.6 µg/m³ Bueng Kum, 9 April: 26.6 µg/m³ Bueng Kum, 10 April: 18.0 µg/m³ Bueng Kum, 11 April: 24.3 µg/m³ Ban Khlong Prawet Ban Khlong Prawet, 2 April: 19.1 µg/m³ Ban Khlong Prawet, 3 April: 23.9 µg/m³ Ban Khlong Prawet, 4 April: 33.7 µg/m³ Ban Khlong Prawet, 5 April: 40.8 µg/m³, 2.0× its usual 20.4 Ban Khlong Prawet, 6 April: no reading Ban Khlong Prawet, 7 April: 33.2 µg/m³ Ban Khlong Prawet, 8 April: 19.8 µg/m³ Ban Khlong Prawet, 9 April: 20.9 µg/m³ Ban Khlong Prawet, 10 April: 15.1 µg/m³ Ban Khlong Prawet, 11 April: 22.0 µg/m³ Bang Khun Thian Bang Khun Thian, 2 April: 43.8 µg/m³ Bang Khun Thian, 3 April: no reading Bang Khun Thian, 4 April: no reading Bang Khun Thian, 5 April: 83.1 µg/m³ Bang Khun Thian, 6 April: 96.7 µg/m³, 2.4× its usual 40.9 Bang Khun Thian, 7 April: 72.9 µg/m³ Bang Khun Thian, 8 April: 41.7 µg/m³ Bang Khun Thian, 9 April: 31.8 µg/m³ Bang Khun Thian, 10 April: 41.8 µg/m³ Bang Khun Thian, 11 April: 50.8 µg/m³ Nong Khaem Nong Khaem, 2 April: 25.3 µg/m³ Nong Khaem, 3 April: 33.9 µg/m³ Nong Khaem, 4 April: 45.1 µg/m³ Nong Khaem, 5 April: 50.0 µg/m³ Nong Khaem, 6 April: 60.9 µg/m³, 2.4× its usual 25.0 Nong Khaem, 7 April: 46.9 µg/m³ Nong Khaem, 8 April: 22.0 µg/m³ Nong Khaem, 9 April: 19.5 µg/m³ Nong Khaem, 10 April: 18.9 µg/m³ Nong Khaem, 11 April: 27.6 µg/m³ Nakhon Pathom Nakhon Pathom, 2 April: 24.8 µg/m³ Nakhon Pathom, 3 April: 31.5 µg/m³ Nakhon Pathom, 4 April: 39.2 µg/m³ Nakhon Pathom, 5 April: 43.3 µg/m³ Nakhon Pathom, 6 April: 54.4 µg/m³, 2.3× its usual 24.0 Nakhon Pathom, 7 April: 41.1 µg/m³ Nakhon Pathom, 8 April: 21.2 µg/m³ Nakhon Pathom, 9 April: 20.0 µg/m³ Nakhon Pathom, 10 April: 21.1 µg/m³ Nakhon Pathom, 11 April: 25.9 µg/m³ Samut Sakhon Samut Sakhon, 2 April: 16.3 µg/m³ Samut Sakhon, 3 April: 24.5 µg/m³ Samut Sakhon, 4 April: 35.7 µg/m³ Samut Sakhon, 5 April: 40.3 µg/m³ Samut Sakhon, 6 April: 52.0 µg/m³, 2.4× its usual 22.0 Samut Sakhon, 7 April: 33.1 µg/m³ Samut Sakhon, 8 April: 14.0 µg/m³ Samut Sakhon, 9 April: no reading Samut Sakhon, 10 April: 13.5 µg/m³ Samut Sakhon, 11 April: 22.6 µg/m³ Mueang Nonthaburi Mueang Nonthaburi, 2 April: 20.6 µg/m³ Mueang Nonthaburi, 3 April: 28.0 µg/m³ Mueang Nonthaburi, 4 April: 36.9 µg/m³ Mueang Nonthaburi, 5 April: 43.5 µg/m³ Mueang Nonthaburi, 6 April: 49.7 µg/m³, 2.1× its usual 23.4 Mueang Nonthaburi, 7 April: 37.2 µg/m³ Mueang Nonthaburi, 8 April: 18.2 µg/m³ Mueang Nonthaburi, 9 April: 17.9 µg/m³ Mueang Nonthaburi, 10 April: 16.5 µg/m³ Mueang Nonthaburi, 11 April: 23.3 µg/m³ Bangkok Bangkok, 2 April: 23.0 µg/m³ Bangkok, 3 April: 28.8 µg/m³ Bangkok, 4 April: 40.9 µg/m³ Bangkok, 5 April: 46.8 µg/m³ Bangkok, 6 April: 48.2 µg/m³, 2.1× its usual 23.1 Bangkok, 7 April: 40.7 µg/m³ Bangkok, 8 April: 23.1 µg/m³ Bangkok, 9 April: 21.2 µg/m³ Bangkok, 10 April: 18.0 µg/m³ Bangkok, 11 April: 25.7 µg/m³ Mae Sai Mae Sai, 2 April: 296.0 µg/m³ Mae Sai, 3 April: 172.0 µg/m³ Mae Sai, 4 April: 198.0 µg/m³ Mae Sai, 5 April: 229.0 µg/m³ Mae Sai, 6 April: no reading Mae Sai, 7 April: 345.0 µg/m³, 4.5× its usual 76.4 Mae Sai, 8 April: 326.0 µg/m³, 4.3× its usual 75.3 Mae Sai, 9 April: 249.0 µg/m³ Mae Sai, 10 April: 163.0 µg/m³ Mae Sai, 11 April: 184.0 µg/m³ Phayao Phayao, 2 April: 146.0 µg/m³ Phayao, 3 April: 99.0 µg/m³ Phayao, 4 April: 112.0 µg/m³ Phayao, 5 April: 145.0 µg/m³ Phayao, 6 April: no reading Phayao, 7 April: 236.0 µg/m³, 3.2× its usual 72.8 Phayao, 8 April: 186.0 µg/m³, 2.6× its usual 71.9 Phayao, 9 April: no reading Phayao, 10 April: no reading Phayao, 11 April: 93.3 µg/m³ Chiang Rai Chiang Rai, 2 April: 202.0 µg/m³ Chiang Rai, 3 April: 124.0 µg/m³ Chiang Rai, 4 April: 117.0 µg/m³ Chiang Rai, 5 April: 118.0 µg/m³ Chiang Rai, 6 April: no reading Chiang Rai, 7 April: 228.0 µg/m³, 3.4× its usual 66.1 Chiang Rai, 8 April: 227.0 µg/m³, 3.5× its usual 65.2 Chiang Rai, 9 April: 169.0 µg/m³ Chiang Rai, 10 April: 126.0 µg/m³ Chiang Rai, 11 April: 140.0 µg/m³ Nan Nan, 2 April: 116.0 µg/m³ Nan, 3 April: 90.3 µg/m³ Nan, 4 April: 99.6 µg/m³ Nan, 5 April: 139.0 µg/m³ Nan, 6 April: no reading Nan, 7 April: 228.0 µg/m³, 3.0× its usual 75.7 Nan, 8 April: 161.0 µg/m³, 2.1× its usual 77.1 Nan, 9 April: no reading Nan, 10 April: no reading Nan, 11 April: 90.0 µg/m³ Chiang Mai Chiang Mai, 2 April: 180.0 µg/m³ Chiang Mai, 3 April: 97.4 µg/m³ Chiang Mai, 4 April: 93.8 µg/m³ Chiang Mai, 5 April: 128.5 µg/m³ Chiang Mai, 6 April: no reading Chiang Mai, 7 April: 223.0 µg/m³, 3.5× its usual 63.2 Chiang Mai, 8 April: 188.0 µg/m³, 3.0× its usual 63.0 Chiang Mai, 9 April: 134.0 µg/m³ Chiang Mai, 10 April: 115.0 µg/m³ Chiang Mai, 11 April: 120.0 µg/m³ Loei Loei, 2 April: 77.4 µg/m³ Loei, 3 April: 80.5 µg/m³ Loei, 4 April: 85.1 µg/m³ Loei, 5 April: 104.0 µg/m³ Loei, 6 April: no reading Loei, 7 April: 215.0 µg/m³, 4.2× its usual 50.7 Loei, 8 April: 212.0 µg/m³, 4.2× its usual 50.7 Loei, 9 April: 80.3 µg/m³ Loei, 10 April: 68.7 µg/m³ Loei, 11 April: 72.7 µg/m³ Lampang Lampang, 2 April: 118.0 µg/m³ Lampang, 3 April: 77.0 µg/m³ Lampang, 4 April: 80.9 µg/m³ Lampang, 5 April: 120.0 µg/m³ Lampang, 6 April: no reading Lampang, 7 April: 182.0 µg/m³, 2.7× its usual 67.6 Lampang, 8 April: 147.0 µg/m³, 2.2× its usual 67.9 Lampang, 9 April: no reading Lampang, 10 April: no reading Lampang, 11 April: 86.7 µg/m³ Lamphun Lamphun, 2 April: 130.0 µg/m³ Lamphun, 3 April: 72.0 µg/m³ Lamphun, 4 April: 69.4 µg/m³ Lamphun, 5 April: 96.6 µg/m³ Lamphun, 6 April: no reading Lamphun, 7 April: 176.0 µg/m³, 2.6× its usual 67.8 Lamphun, 8 April: 135.0 µg/m³, 2.0× its usual 67.1 Lamphun, 9 April: no reading Lamphun, 10 April: no reading Lamphun, 11 April: 82.0 µg/m³ Tha Bo Tha Bo, 2 April: 71.3 µg/m³ Tha Bo, 3 April: 44.8 µg/m³ Tha Bo, 4 April: 130.0 µg/m³ Tha Bo, 5 April: 111.0 µg/m³ Tha Bo, 6 April: 182.0 µg/m³ Tha Bo, 7 April: 146.0 µg/m³, 2.8× its usual 51.7 Tha Bo, 8 April: 50.3 µg/m³ Tha Bo, 9 April: 37.0 µg/m³ Tha Bo, 10 April: 66.4 µg/m³ Tha Bo, 11 April: 90.7 µg/m³ Vientiane Vientiane, 2 April: 71.3 µg/m³ Vientiane, 3 April: 44.8 µg/m³ Vientiane, 4 April: 130.0 µg/m³ Vientiane, 5 April: 111.0 µg/m³ Vientiane, 6 April: 182.0 µg/m³ Vientiane, 7 April: 146.0 µg/m³, 2.6× its usual 55.1 Vientiane, 8 April: 50.3 µg/m³ Vientiane, 9 April: 37.0 µg/m³ Vientiane, 10 April: 66.4 µg/m³ Vientiane, 11 April: 90.7 µg/m³ Phrae Phrae, 2 April: 78.6 µg/m³ Phrae, 3 April: 63.0 µg/m³ Phrae, 4 April: 77.0 µg/m³ Phrae, 5 April: 115.0 µg/m³ Phrae, 6 April: no reading Phrae, 7 April: 135.0 µg/m³, 2.4× its usual 56.1 Phrae, 8 April: 99.9 µg/m³ Phrae, 9 April: no reading Phrae, 10 April: no reading Phrae, 11 April: 67.3 µg/m³ Bueng Kan Bueng Kan, 2 April: 49.7 µg/m³ Bueng Kan, 3 April: 33.3 µg/m³ Bueng Kan, 4 April: 46.7 µg/m³ Bueng Kan, 5 April: 101.0 µg/m³ Bueng Kan, 6 April: no reading Bueng Kan, 7 April: 132.0 µg/m³, 2.7× its usual 48.2 Bueng Kan, 8 April: 56.2 µg/m³ Bueng Kan, 9 April: 33.4 µg/m³ Bueng Kan, 10 April: 42.6 µg/m³ Bueng Kan, 11 April: 58.2 µg/m³ Pakxan Pakxan, 2 April: 49.7 µg/m³ Pakxan, 3 April: 33.3 µg/m³ Pakxan, 4 April: 46.7 µg/m³ Pakxan, 5 April: 101.0 µg/m³ Pakxan, 6 April: no reading Pakxan, 7 April: 132.0 µg/m³, 2.7× its usual 48.2 Pakxan, 8 April: 56.2 µg/m³ Pakxan, 9 April: 33.4 µg/m³ Pakxan, 10 April: 42.6 µg/m³ Pakxan, 11 April: 58.2 µg/m³ Sukhothai Sukhothai, 2 April: 68.5 µg/m³ Sukhothai, 3 April: 43.3 µg/m³ Sukhothai, 4 April: 41.9 µg/m³ Sukhothai, 5 April: 50.1 µg/m³ Sukhothai, 6 April: no reading Sukhothai, 7 April: 124.0 µg/m³, 2.6× its usual 47.1 Sukhothai, 8 April: 89.8 µg/m³ Sukhothai, 9 April: 51.1 µg/m³ Sukhothai, 10 April: 73.0 µg/m³ Sukhothai, 11 April: 69.0 µg/m³ Nong Bua Lamphu Nong Bua Lamphu, 2 April: 48.7 µg/m³ Nong Bua Lamphu, 3 April: 40.1 µg/m³ Nong Bua Lamphu, 4 April: 50.9 µg/m³ Nong Bua Lamphu, 5 April: 70.1 µg/m³ Nong Bua Lamphu, 6 April: no reading Nong Bua Lamphu, 7 April: 113.0 µg/m³, 2.9× its usual 39.4 Nong Bua Lamphu, 8 April: 87.0 µg/m³, 2.2× its usual 39.4 Nong Bua Lamphu, 9 April: no reading Nong Bua Lamphu, 10 April: 50.3 µg/m³ Nong Bua Lamphu, 11 April: 53.1 µg/m³ Ban Thai Tan Ban Thai Tan, 2 April: 32.9 µg/m³ Ban Thai Tan, 3 April: 41.5 µg/m³ Ban Thai Tan, 4 April: 51.0 µg/m³ Ban Thai Tan, 5 April: 52.0 µg/m³ Ban Thai Tan, 6 April: no reading Ban Thai Tan, 7 April: 71.7 µg/m³, 2.1× its usual 34.4 Ban Thai Tan, 8 April: 58.5 µg/m³ Ban Thai Tan, 9 April: no reading Ban Thai Tan, 10 April: no reading Ban Thai Tan, 11 April: 40.3 µg/m³ Hua Hin Hua Hin, 2 April: 24.3 µg/m³ Hua Hin, 3 April: 28.0 µg/m³ Hua Hin, 4 April: 41.2 µg/m³ Hua Hin, 5 April: 35.3 µg/m³ Hua Hin, 6 April: no reading Hua Hin, 7 April: 43.7 µg/m³, 2.0× its usual 21.4 Hua Hin, 8 April: 31.2 µg/m³ Hua Hin, 9 April: 22.2 µg/m³ Hua Hin, 10 April: 19.0 µg/m³ Hua Hin, 11 April: 27.9 µg/m³ Chiang Khong Chiang Khong, 2 April: 197.0 µg/m³ Chiang Khong, 3 April: 144.0 µg/m³ Chiang Khong, 4 April: 166.0 µg/m³ Chiang Khong, 5 April: 182.0 µg/m³ Chiang Khong, 6 April: no reading Chiang Khong, 7 April: no reading Chiang Khong, 8 April: 317.0 µg/m³, 3.7× its usual 86.8 Chiang Khong, 9 April: no reading Chiang Khong, 10 April: no reading Chiang Khong, 11 April: 142.0 µg/m³ Ban Houakhoua Ban Houakhoua, 2 April: 197.0 µg/m³ Ban Houakhoua, 3 April: 144.0 µg/m³ Ban Houakhoua, 4 April: 166.0 µg/m³ Ban Houakhoua, 5 April: 182.0 µg/m³ Ban Houakhoua, 6 April: no reading Ban Houakhoua, 7 April: no reading Ban Houakhoua, 8 April: 317.0 µg/m³, 3.7× its usual 86.8 Ban Houakhoua, 9 April: no reading Ban Houakhoua, 10 April: no reading Ban Houakhoua, 11 April: 142.0 µg/m³ Udon Thani Udon Thani, 2 April: 52.0 µg/m³ Udon Thani, 3 April: 38.1 µg/m³ Udon Thani, 4 April: 50.9 µg/m³ Udon Thani, 5 April: no reading Udon Thani, 6 April: no reading Udon Thani, 7 April: no reading Udon Thani, 8 April: 82.4 µg/m³, 2.1× its usual 39.3 Udon Thani, 9 April: 35.2 µg/m³ Udon Thani, 10 April: 40.3 µg/m³ Udon Thani, 11 April: 51.3 µg/m³ 2 Apr 3 4 5 6 7 8 9 10 11 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
Mae Sai Chiang Rai, Thailand 2 7 April 76.4 4.5× Loei Loei, Thailand 2 7 April 50.7 4.2× Chiang Khong Chiang Rai, Thailand 1 8 April 86.8 3.7× Ban Houakhoua Bokeo, Laos 1 8 April 86.8 3.7× Chiang Mai Chiang Mai, Thailand 2 7 April 63.2 3.5× Chiang Rai Chiang Rai, Thailand 2 7 April 66.1 3.4× Phayao Phayao, Thailand 2 7 April 72.8 3.2× Nan Nan, Thailand 2 7 April 75.7 3.0× Nong Bua Lamphu Nong Bua Lamphu, Thailand 2 7 April 39.4 2.9× Tha Bo Nong Khai, Thailand 1 7 April 51.7 2.8× Lampang Lampang, Thailand 2 7 April 67.6 2.7× Bueng Kan Bueng Kan, Thailand 1 7 April 48.2 2.7× Pakxan Bolikhamsai, Laos 1 7 April 48.2 2.7× Lamphun Lamphun, Thailand 2 7 April 67.8 2.6× Vientiane Vientiane Prefecture, Laos 1 7 April 55.1 2.6× Sukhothai Sukhothai, Thailand 1 7 April 47.1 2.6× Phrae Phrae, Thailand 1 7 April 56.1 2.4× Bang Khun Thian Bangkok, Thailand 1 6 April 40.9 2.4× Nong Khaem Bangkok, Thailand 1 6 April 25.0 2.4× Samut Sakhon Samut Sakhon, Thailand 1 6 April 22.0 2.4× Nakhon Pathom Nakhon Pathom, Thailand 1 6 April 24.0 2.3× Samut Prakan Samut Prakan, Thailand 2 5 April 20.0 2.3× Udon Thani Udon Thani, Thailand 1 8 April 39.3 2.1× Ban Thai Tan Ang Thong, Thailand 1 7 April 34.4 2.1× Mueang Nonthaburi Nonthaburi, Thailand 1 6 April 23.4 2.1× Bangkok Bangkok, Thailand 1 6 April 23.1 2.1× Ban Samae Dam Bangkok, Thailand 1 5 April 23.8 2.0× Bueng Kum Bangkok, Thailand 1 5 April 22.0 2.0× Hua Hin Prachuap Khiri Khan, Thailand 1 7 April 21.4 2.0× Ban Khlong Prawet Bangkok, Thailand 1 5 April 20.4 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 9 of 24 episodes in Thailand and Laos since our records began, by cities reached.
Thailand and Laos, March 2025 56 Thailand, February 2024 52 Northern Thailand, January 2025 51 Thailand and Laos, April and May 2024 47 Northern Thailand and Laos, 20 to 22 May 2023 44 Thailand, April 2023 36 Northern Thailand and Laos, January and February 2023 36 Northern Thailand and Laos, 16 to 18 May 2023 32 Northern Thailand and Laos around Bangkok, 5 to 8 April 2023 30 Thailand and Laos, October 2024 24 Thailand and Laos, November and December 2025 23 Thailand, 12 to 13 February 2025 18 Bars: cities reached; colour: the level of the episode's highest daily reading. All 24 .
Use this page SmogRank, Northern Thailand and Laos around Bangkok, 5 to 8 April 2023: 30 cities with PM2.5 at twice their usual or more, 5 to 8 April 2023, smogrank.com/episodes/2023-04-05-northern-thailand-and-laos-bangkok (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.
