Thailand Rainy Season Statistics 2026: Rain by Month at 22 Weather Stations
Inland Thailand gets most of its rain between May and October: at the 10 inland stations (North, Northeast, Bangkok and Kanchanaburi), those months account for between 83% (Kanchanaburi) and 94% (Mae Sot) of the year's total.1 Nationally, 15 of the 22 stations see their wettest month in July, August or September.1 The 4 stations whose wettest month is November are all on or near the Gulf of Thailand coast south of Hua Hin: Chumphon, Koh Samui, Songkhla and Hat Yai.1
Key Thailand rainy season statistics
The 2026 ThingsToDoIn Thailand Rainy Season Index found that Trat, the mainland gateway to Koh Chang, averages 1,024.1 mm of rain in July, the wettest month at any of the 22 stations and more than Hua Hin receives in an entire year (935.9 mm).1
The 2026 ThingsToDoIn Thailand Rainy Season Index found that Koh Samui receives 50% of its yearly rain, 1,002.6 mm out of 1,994.3 mm, in October, November and December.1
The 2026 ThingsToDoIn Thailand Rainy Season Index found that May to October delivers 76% of Phuket's annual rain but just 45% of Koh Samui's.1
The 2026 ThingsToDoIn Thailand Rainy Season Index found that Hua Hin, at 935.9 mm a year, is the driest station in the index, with October (250.4 mm) its only month above 150 mm.1
The 2026 ThingsToDoIn Thailand Rainy Season Index found that Bangkok averages 18.0 days with at least 1 mm of rain in September, compared with 1.0 in December.1
- Trat is the wettest station in the index with 4,926.5 mm a year, and Ranong comes next at 4,183.1 mm.1
- Phuket averages 240.2 mm of rain in July, while Koh Samui gets 117.0 mm.1
- In December, every one of the 8 stations in the North and Northeast averages 20.6 mm of rain or less.1
- Chiang Mai gets 110.8 hours of sunshine in August, its dullest month, compared with 267.9 hours in March.1
- No station has more rain days in a month than Trat in July and August, with 24.6 days each of at least 1 mm.1
- Even in each destination's wettest month, the clear-sky peak UV index we measured was 10 or higher at all 16 destinations where we measure UV.2,1
Thailand rainfall by month at 22 weather stations
The table gives the average rainfall for every month at each station, grouped by region.
| Destination | Region | Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec | Year |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Chiang Mai | North | 11.3 | 9.6 | 20.4 | 54.3 | 167.5 | 118.2 | 148.6 | 223.3 | 207.2 | 123.8 | 40.9 | 14.1 | 1,139.2 |
| Chiang Rai | North | 16.5 | 12.7 | 34.5 | 92.6 | 226.5 | 186.2 | 317.6 | 372.9 | 275.1 | 123.5 | 44.8 | 20.6 | 1,723.5 |
| Mae Hong Son | North | 11.0 | 5.5 | 19.2 | 59.6 | 168.9 | 180.1 | 226.4 | 258.5 | 200.5 | 116.8 | 39.6 | 10.9 | 1,297.0 |
| Mae Sot | North | 7.5 | 6.8 | 20.9 | 36.1 | 153.5 | 246.8 | 372.9 | 353.6 | 204.7 | 91.6 | 19.4 | 6.7 | 1,520.5 |
| Khon Kaen | Northeast (Isan) | 6.0 | 17.3 | 38.0 | 94.6 | 155.0 | 145.7 | 177.9 | 222.2 | 246.0 | 102.1 | 21.5 | 5.1 | 1,231.4 |
| Udon Thani | Northeast (Isan) | 6.4 | 21.2 | 50.2 | 73.0 | 188.3 | 218.5 | 224.8 | 298.9 | 249.5 | 94.3 | 14.0 | 5.8 | 1,444.9 |
| Nong Khai | Northeast (Isan) | 10.6 | 18.3 | 43.8 | 83.9 | 232.1 | 252.7 | 321.9 | 346.5 | 268.8 | 88.4 | 15.6 | 8.2 | 1,690.8 |
| Ubon Ratchathani | Northeast (Isan) | 3.2 | 11.3 | 28.6 | 82.6 | 222.9 | 236.9 | 293.8 | 291.4 | 314.4 | 112.1 | 21.8 | 5.0 | 1,624.0 |
| Bangkok | Central and West | 23.6 | 21.4 | 51.0 | 93.3 | 216.8 | 198.5 | 189.7 | 227.1 | 335.9 | 288.7 | 44.6 | 11.6 | 1,702.2 |
| Kanchanaburi | Central and West | 7.6 | 18.3 | 39.4 | 66.4 | 139.4 | 98.9 | 106.0 | 100.6 | 219.0 | 206.3 | 44.6 | 7.2 | 1,053.7 |
| Pattaya | East coast | 16.3 | 19.9 | 47.3 | 67.9 | 121.1 | 132.1 | 103.6 | 91.2 | 213.6 | 224.5 | 56.6 | 11.7 | 1,105.8 |
| Trat (for Koh Chang) | East coast | 51.1 | 81.5 | 140.0 | 196.0 | 419.9 | 777.2 | 1,024.1 | 969.7 | 816.4 | 337.6 | 85.2 | 27.8 | 4,926.5 |
| Hua Hin | Western Gulf coast | 25.0 | 13.8 | 50.5 | 46.5 | 95.5 | 82.4 | 90.2 | 67.1 | 129.8 | 250.4 | 72.8 | 11.9 | 935.9 |
| Chumphon (for Koh Tao) | Western Gulf coast | 96.7 | 51.7 | 110.3 | 93.2 | 171.0 | 163.0 | 195.0 | 199.2 | 178.9 | 247.2 | 258.6 | 172.6 | 1,937.4 |
| Koh Samui | Southern Gulf coast | 126.8 | 64.3 | 115.8 | 82.9 | 131.6 | 133.6 | 117.0 | 102.2 | 117.5 | 294.9 | 444.6 | 263.1 | 1,994.3 |
| Songkhla | Southern Gulf coast | 127.2 | 54.9 | 71.3 | 85.8 | 114.8 | 102.7 | 95.1 | 137.8 | 123.3 | 279.8 | 587.9 | 468.3 | 2,248.9 |
| Hat Yai | Southern Gulf coast | 88.1 | 29.9 | 77.4 | 116.4 | 128.5 | 121.0 | 100.5 | 123.8 | 146.8 | 224.3 | 324.3 | 275.0 | 1,756.0 |
| Ranong | Andaman coast | 41.1 | 19.8 | 77.6 | 154.2 | 485.9 | 638.0 | 706.3 | 771.5 | 678.8 | 421.3 | 130.1 | 58.5 | 4,183.1 |
| Phuket | Andaman coast | 49.9 | 24.0 | 80.7 | 135.1 | 236.9 | 249.4 | 240.2 | 308.7 | 350.4 | 336.0 | 178.2 | 82.0 | 2,271.5 |
| Koh Lanta | Andaman coast | 31.0 | 24.1 | 69.0 | 121.6 | 227.5 | 285.9 | 288.5 | 342.0 | 319.4 | 297.5 | 148.4 | 64.6 | 2,219.5 |
| Trang | Andaman coast | 57.3 | 25.6 | 101.6 | 149.0 | 216.7 | 214.7 | 254.4 | 286.0 | 287.0 | 283.3 | 226.2 | 152.2 | 2,254.0 |
| Satun | Andaman coast | 43.6 | 40.6 | 133.9 | 210.3 | 228.7 | 189.7 | 230.4 | 277.8 | 334.2 | 343.8 | 217.8 | 118.4 | 2,369.2 |
Wettest month in Thailand by region
July, August or September is the wettest month at 15 of the 22 stations.1 The 4 stations whose wettest month is November are all on or near the Gulf of Thailand coast south of Hua Hin: Chumphon, Koh Samui, Songkhla and Hat Yai.1 Trat, the mainland gateway to Koh Chang, averages 1,024.1 mm in July, the wettest month at any of the 22 stations.1 At 4,926.5 mm a year it is also the wettest station overall, ahead of Ranong at 4,183.1 mm.1 Counting months that average 150 mm or more, the rainy season runs for 1 month at Hua Hin and as long as 8 months at Chumphon, Trang and Satun.1
Koh Samui vs Phuket rainy season
Phuket and Koh Samui take most of their rain at different times of year.1 Between May and October, Phuket gets 76% of its annual rain, while Koh Samui gets only 45%.1 In July, Phuket averages 240.2 mm against 117.0 mm on Koh Samui.1 Koh Samui's wet season arrives later: 1,002.6 mm of its 1,994.3 mm year, or 50%, falls in October, November and December.1
How many days does it rain in Thailand's rainy season?
In Bangkok, September averages 18.0 days with at least 1 mm of rain, against 1.0 in December.1 Trat has the most rain days of any station: 24.6 days with at least 1 mm in July and again in August.1 The table below shows rain days by month for every station.
| Destination | Region | Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Chiang Mai | North | 1.0 | 0.7 | 2.1 | 4.7 | 12.0 | 11.6 | 14.4 | 17.1 | 14.7 | 9.1 | 3.0 | 1.2 |
| Chiang Rai | North | 1.5 | 1.2 | 2.9 | 7.9 | 14.5 | 14.6 | 19.6 | 20.5 | 14.7 | 8.3 | 3.5 | 1.9 |
| Mae Hong Son | North | 1.0 | 0.5 | 1.4 | 4.3 | 13.6 | 17.0 | 20.4 | 20.7 | 15.5 | 10.0 | 3.4 | 1.2 |
| Mae Sot | North | 0.6 | 0.5 | 1.8 | 3.3 | 12.5 | 20.5 | 23.3 | 23.7 | 16.6 | 8.2 | 1.5 | 0.5 |
| Khon Kaen | Northeast (Isan) | 0.8 | 1.6 | 3.3 | 5.9 | 11.2 | 10.4 | 12.4 | 14.4 | 15.1 | 6.8 | 1.6 | 0.5 |
| Udon Thani | Northeast (Isan) | 0.9 | 1.9 | 3.7 | 5.2 | 12.9 | 14.7 | 16.1 | 18.1 | 14.2 | 6.1 | 1.2 | 0.5 |
| Nong Khai | Northeast (Isan) | 1.1 | 1.6 | 3.9 | 6.2 | 13.5 | 15.7 | 18.0 | 18.9 | 14.5 | 5.6 | 1.4 | 0.6 |
| Ubon Ratchathani | Northeast (Isan) | 0.3 | 0.9 | 2.6 | 5.2 | 12.2 | 14.0 | 16.4 | 17.8 | 16.3 | 7.7 | 1.7 | 0.3 |
| Bangkok | Central and West | 1.9 | 1.9 | 3.4 | 5.4 | 12.4 | 13.4 | 14.1 | 15.6 | 18.0 | 14.4 | 3.8 | 1.0 |
| Kanchanaburi | Central and West | 0.8 | 1.1 | 2.6 | 4.2 | 10.1 | 10.0 | 10.6 | 11.0 | 13.8 | 12.0 | 3.5 | 0.8 |
| Pattaya | East coast | 1.6 | 1.8 | 3.3 | 5.0 | 9.0 | 9.8 | 9.5 | 9.1 | 13.2 | 14.4 | 4.0 | 1.5 |
| Trat (for Koh Chang) | East coast | 3.5 | 5.6 | 9.6 | 11.7 | 18.8 | 23.3 | 24.6 | 24.6 | 22.5 | 17.4 | 6.8 | 2.4 |
| Hua Hin | Western Gulf coast | 1.3 | 0.8 | 2.2 | 2.7 | 8.5 | 9.2 | 9.7 | 9.7 | 10.6 | 12.7 | 4.2 | 1.3 |
| Chumphon (for Koh Tao) | Western Gulf coast | 5.5 | 3.1 | 5.3 | 5.8 | 13.0 | 14.2 | 16.5 | 16.0 | 15.4 | 15.9 | 11.9 | 6.9 |
| Koh Samui | Southern Gulf coast | 8.5 | 4.3 | 4.7 | 6.1 | 11.0 | 10.3 | 10.7 | 10.5 | 10.6 | 15.8 | 16.5 | 11.6 |
| Songkhla | Southern Gulf coast | 7.5 | 4.5 | 5.3 | 6.3 | 9.8 | 8.9 | 9.2 | 10.5 | 11.4 | 16.2 | 20.3 | 17.7 |
| Hat Yai | Southern Gulf coast | 6.2 | 2.8 | 5.0 | 8.7 | 11.1 | 9.8 | 10.4 | 10.9 | 12.7 | 16.8 | 18.3 | 15.2 |
| Ranong | Andaman coast | 3.1 | 2.4 | 5.4 | 10.2 | 20.4 | 21.6 | 23.0 | 23.8 | 22.8 | 19.2 | 10.5 | 5.3 |
| Phuket | Andaman coast | 4.3 | 2.2 | 6.0 | 9.6 | 15.7 | 15.9 | 16.3 | 16.9 | 18.9 | 19.4 | 12.9 | 7.8 |
| Koh Lanta | Andaman coast | 2.6 | 1.8 | 4.8 | 9.0 | 14.2 | 15.1 | 14.9 | 14.8 | 17.0 | 17.9 | 12.3 | 7.8 |
| Trang | Andaman coast | 4.6 | 2.4 | 6.0 | 10.0 | 15.0 | 14.2 | 15.4 | 16.7 | 17.4 | 18.9 | 14.9 | 10.5 |
| Satun | Andaman coast | 4.1 | 3.5 | 8.3 | 13.8 | 14.9 | 13.0 | 14.1 | 15.7 | 17.3 | 20.4 | 15.4 | 10.4 |
When is the dry season in Thailand?
In December, all 8 stations in the North and Northeast average 20.6 mm of rain or less.1 At the 10 inland stations (North, Northeast, Bangkok and Kanchanaburi), May to October accounts for between 83% (Kanchanaburi) and 94% (Mae Sot) of annual rain.1 Hua Hin is the driest station in the index at 935.9 mm a year, and October (250.4 mm) is the only month there above 150 mm.1
To plan around the weather, see our guide to when to visit Thailand, and compare Thailand in December with Thailand in September.
Sunshine and UV in the rainy season
Chiang Mai gets 110.8 hours of sunshine in August, its dullest month, compared with 267.9 hours in March.1 Even in each destination's wettest month, the clear-sky peak UV index we measured reached 10 or higher at all 16 destinations where we measure it.2,1 The WHO scale rates a UV index of 8 to 10 as very high and 11 or more as extreme.3
| Destination | Region | Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Chiang Mai | North | 8 | 9 | 10 | 11 | 12 | 13 | 13 | 13 | 12 | 10 | 8 | 7 |
| Chiang Rai | North | 7 | 9 | 9 | 10 | 11 | 12 | 13 | 13 | 12 | 10 | 8 | 7 |
| Mae Sot | North | 8 | 9 | 11 | 11 | 12 | 13 | 13 | 13 | 12 | 10 | 8 | 8 |
| Khon Kaen | Northeast (Isan) | 8 | 10 | 10 | 11 | 11 | 12 | 12 | 12 | 12 | 10 | 9 | 8 |
| Udon Thani | Northeast (Isan) | 8 | 10 | 10 | 10 | 11 | 12 | 12 | 12 | 12 | 10 | 8 | 8 |
| Nong Khai | Northeast (Isan) | 8 | 9 | 10 | 10 | 11 | 12 | 12 | 12 | 12 | 10 | 8 | 7 |
| Ubon Ratchathani | Northeast (Isan) | 9 | 10 | 11 | 11 | 12 | 12 | 12 | 13 | 12 | 10 | 9 | 8 |
| Bangkok | Central and West | 8 | 10 | 11 | 11 | 11 | 12 | 12 | 13 | 12 | 10 | 9 | 8 |
| Kanchanaburi | Central and West | 9 | 10 | 12 | 12 | 12 | 13 | 13 | 13 | 13 | 11 | 9 | 8 |
| Hua Hin | Western Gulf coast | 9 | 10 | 12 | 12 | 12 | 12 | 12 | 13 | 13 | 11 | 9 | 9 |
| Koh Samui | Southern Gulf coast | 10 | 11 | 13 | 13 | 12 | 12 | 12 | 13 | 13 | 12 | 10 | 10 |
| Songkhla | Southern Gulf coast | 11 | 12 | 14 | 13 | 12 | 11 | 12 | 13 | 13 | 12 | 11 | 10 |
| Hat Yai | Southern Gulf coast | 11 | 12 | 14 | 13 | 12 | 11 | 12 | 13 | 13 | 12 | 11 | 10 |
| Phuket | Andaman coast | 11 | 12 | 13 | 13 | 12 | 12 | 12 | 13 | 13 | 12 | 11 | 10 |
| Trang | Andaman coast | 11 | 12 | 13 | 13 | 12 | 12 | 12 | 13 | 13 | 12 | 11 | 10 |
| Satun | Andaman coast | 11 | 12 | 14 | 14 | 12 | 12 | 12 | 13 | 13 | 13 | 11 | 10 |
How we built the index
Station normals are the WMO 1991-2020 averages for the named weather station, not forecasts. A month counts toward the rainy season when it averages 150 mm of rain or more. Rain days are days with at least 1 mm of rain. Trat stands in for Koh Chang and Chumphon for Koh Tao, because those islands have no WMO normals station. UV is the clear-sky peak, so it is an upper bound: cloud lowers the UV that reaches the ground. Every number on this page links to its source in the list below.
Sources
- World Meteorological Organization, Climate Normals for 1991-2020, single station data sheets for Thailand (NOAA NCEI archive, accession 0253808)
- Chiang Mai: WMO 48327 Chiang Mai (CSV)
- Chiang Rai: WMO 48303 Chiang Rai (CSV)
- Mae Hong Son: WMO 48300 Mae Hong Son (CSV)
- Mae Sot: WMO 48375 Mae Sot (CSV)
- Khon Kaen: WMO 48381 Khon Kaen (CSV)
- Udon Thani: WMO 48354 Udon Thani (CSV)
- Nong Khai: WMO 48352 Nong Khai (CSV)
- Ubon Ratchathani: WMO 48407 Ubon Ratchathani (CSV)
- Bangkok: WMO 48455 Bangkok Metropolis (CSV)
- Kanchanaburi: WMO 48450 Kanchana Buri (CSV)
- Pattaya: WMO 48461 Phatthaya (CSV)
- Trat (for Koh Chang): WMO 48501 Trad (CSV)
- Hua Hin: WMO 48475 Hua Hin (CSV)
- Chumphon (for Koh Tao): WMO 48517 Chumphon (CSV)
- Koh Samui: WMO 48550 Ko Samui (CSV)
- Songkhla: WMO 48568 Songkhla (CSV)
- Hat Yai: WMO 48569 Hat Yai Airport (CSV)
- Ranong: WMO 48532 Ranong (CSV)
- Phuket: WMO 48564 Phuket (CSV)
- Koh Lanta: WMO 48566 Ko Lanta (CSV)
- Trang: WMO 48567 Trang Airport (CSV)
- Satun: WMO 48570 Satun (CSV)
- Copernicus Atmosphere Monitoring Service (CAMS) clear-sky UV index via the Open-Meteo Air Quality API; mean daily peak measured by ThingsToDoIn, 2024-2025
- World Health Organization, Global Solar UV Index: A Practical Guide (2002)
Cite this data
ThingsToDoIn, Thailand Rainy Season Index 2026, https://thingstodointhailand.com/rainy-season/
The data: thailand-rainfall-by-month-1991-2020.csv. You may reuse the CSV with attribution to ThingsToDoIn under CC BY 4.0.