Very heavy rain puts eight provinces on flash-flood alert
Very heavy rain is forecast in eight provinces, with Bangkok facing 70% coverage and small boats in the upper Andaman told to remain ashore
The Thai Meteorological Department (TMD) has warned of rain across 43 provinces on Tuesday (September 1, 2026), with very heavy falls forecast in eight provinces and isolated heavy rain expected in Bangkok and surrounding areas.
Mae Hong Son, Tak, Nakhon Phanom, Amnat Charoen, Ubon Ratchathani, Nakhon Nayok, Prachin Buri and Sa Kaeo face the heaviest rainfall during the 24-hour period from 6am on Tuesday to 6am on Wednesday.
The conditions are being driven by a monsoon trough crossing the North and upper Northeast and extending towards a depression over the southern Chinese coast.
A rather strong south-west monsoon is also prevailing over the Andaman Sea, Thailand and the Gulf of Thailand.
Residents in affected areas have been advised to prepare for heavy to very heavy rain and accumulated rainfall that could trigger flash floods and run-off, particularly on foothill slopes, near waterways and across low-lying land.
The TMD also advised people to avoid routes repeatedly affected by flooding, especially low-lying roads where short-term inundation may occur.
Regional forecast
- North: Thunderstorms are forecast across 70% of the region. Heavy rain is expected in Chiang Mai, Lampang, Lamphun, Uttaradit, Sukhothai, Kamphaeng Phet, Phitsanulok, Phichit and Phetchabun, with very heavy rain in Mae Hong Son and Tak. Temperatures will range from 22-26°C overnight to 28-33°C during the day. South-westerly winds will reach 10-20 kilometres per hour.
- Northeast: Thunderstorms will cover 70% of the region. Heavy rain is forecast in Loei, Bueng Kan, Sakon Nakhon, Chaiyaphum, Mukdahan, Yasothon, Nakhon Ratchasima, Buri Ram, Surin and Si Sa Ket. Nakhon Phanom, Amnat Charoen and Ubon Ratchathani face very heavy rain. Temperatures will range from 23-24°C to 27-32°C, with south-westerly winds of 10-25km/h.
- Central region: Thunderstorms are expected across 60% of the region, with heavy rain in Uthai Thani, Lop Buri, Saraburi and Kanchanaburi. Temperatures will range from 23-25°C to 31-34°C. South-westerly winds will reach 10-25km/h.
- East: Thunderstorms will cover 70% of the region. Rayong, Chanthaburi and Trat face heavy rain, while very heavy falls are forecast in Nakhon Nayok, Prachin Buri and Sa Kaeo. Temperatures will range from 23-27°C to 29-34°C, with south-westerly winds of 20-35km/h. Waves will be about two metres high and exceed two metres during thunderstorms.
- South, east coast: Thunderstorms are forecast across 40% of the region, mainly in Phetchaburi, Prachuap Khiri Khan, Chumphon and Surat Thani. Temperatures will range from 23-26°C to 31-36°C. From Surat Thani northwards, south-westerly winds will reach 20-35km/h, with waves of one to two metres, about two metres offshore and above two metres during thunderstorms. From Nakhon Si Thammarat southwards, winds will reach 15-35km/h, with waves of about one metre, rising to one to two metres offshore and above two metres during thunderstorms.
- South, west coast: Thunderstorms are expected across 40% of the region, mainly in Ranong, Phang Nga, Trang and Satun. Temperatures will range from 23-27°C to 31-35°C. From Phuket northwards, south-westerly winds will reach 20-40km/h and waves will rise to two to three metres, exceeding three metres during thunderstorms. From Krabi southwards, winds will reach 20-35km/h and waves will be about two metres, exceeding two metres during thunderstorms.
- Bangkok and surrounding provinces: Thunderstorms are forecast across 70% of the area, with isolated heavy rain. Temperatures will range from 25-27°C to 31-34°C, with south-westerly winds of 10-25km/h.
Small boats told to remain ashore
Conditions in the upper Andaman Sea will remain rough, with waves of two to three metres and heights exceeding three metres during thunderstorms.
Waves in the lower Andaman Sea and upper Gulf of Thailand will be about two metres, rising above two metres in stormy areas.
Mariners in the Andaman Sea and Gulf of Thailand should proceed cautiously and avoid thunderstorms. Small boats in the upper Andaman Sea should remain ashore.
Tropical Storm Saudel to approach Taiwan
The depression over the upper South China Sea, east of Hainan Island, has strengthened into Tropical Storm Saudel.
The storm is forecast to move near Taiwan between Thursday and Friday (September 3-4). Travellers heading to affected areas should check the latest weather conditions before departure.
The TMD said the storm would not move into Thailand.
