Thailand faces heavy rain and flood risk through Wednesday

Heavy or very heavy rain is forecast in 34 provinces on Tuesday (September 1, 2026) and 29 provinces on Wednesday, raising the risk of flash floods, overflowing waterways and landslides, the Thai Meteorological Department (TMD) has warned.

Eight provinces are expected to receive very heavy rain on Tuesday, while Amnat Charoen and Ubon Ratchathani will remain at the highest warning level on Wednesday.

The warning was contained in the department’s advisory No.12 (179/2026), issued at 5am on Tuesday. The most intense rainfall is forecast in the western North and Central region, the upper and eastern Northeast, and the East.

The monsoon trough is extending across the North and upper Northeast into Tropical Storm Saudel over the upper South China Sea. A relatively strong southwest monsoon is also prevailing over the Andaman Sea, Thailand and the Gulf of Thailand, bringing increased rainfall to several regions.

People in vulnerable areas should monitor accumulated rainfall, particularly those living near waterways, foothills and low-lying land. The TMD also advised the public to plan journeys carefully and avoid routes that experience repeated flooding.

Eight provinces face very heavy rain on Tuesday

The provinces forecast to receive very heavy rain on September 1 are:

• North: Mae Hong Son and Tak
• Northeast: Nakhon Phanom, Amnat Charoen and Ubon Ratchathani
• East: Nakhon Nayok, Prachin Buri and Sa Kaeo

Heavy rain is forecast in a further 26 provinces:

• North: Chiang Mai, Lampang, Lamphun, Uttaradit, Sukhothai, Kamphaeng Phet, Phitsanulok, Phichit and Phetchabun
• Northeast: Loei, Bueng Kan, Sakon Nakhon, Chaiyaphum, Mukdahan, Yasothon, Nakhon Ratchasima, Buri Ram, Surin and Si Sa Ket
• Central: Uthai Thani, Lop Buri, Saraburi and Kanchanaburi
• East: Rayong, Chanthaburi and Trat

Heavy rain shifts across 29 provinces on Wednesday

Very heavy rain is forecast in the northeastern provinces of Amnat Charoen and Ubon Ratchathani on September 2.

A further 27 provinces are expected to receive heavy rain:

• North: Chiang Mai, Chiang Rai, Lampang, Phayao, Nan, Phrae, Uttaradit and Phitsanulok
• Northeast: Loei, Nong Khai, Bueng Kan, Nong Bua Lam Phu, Udon Thani, Sakon Nakhon, Nakhon Phanom, Mukdahan, Kalasin, Khon Kaen, Maha Sarakham, Roi Et, Yasothon, Surin and Si Sa Ket
• East: Chanthaburi and Trat
• South: Ranong and Phang Nga

Bangkok and upper Thailand face widespread storms

The regional forecast from 6am on Tuesday to 6am on Wednesday is as follows:

• North: Thunderstorms across 70% of the region, with heavy to very heavy rain in some areas. Temperatures will range from lows of 22-26 degrees Celsius to highs of 28-33°C. Southwesterly winds will reach 10-20 kilometres per hour.
• Northeast: Thunderstorms across 70% of the region, with isolated heavy to very heavy rain. Temperatures will range from 23-24°C to 27-32°C, with southwesterly winds of 10-25kph.
• Central region: Thunderstorms across 60% of the region, with isolated heavy rain. Temperatures will range from 23-25°C to 31-34°C, with southwesterly winds of 10-25kph.
• East: Thunderstorms across 70% of the region, with heavy to very heavy rain in some areas. Temperatures will range from 23-27°C to 29-34°C. Southwesterly winds will reach 20-35kph, with waves of about two metres and higher than two metres during thunderstorms.
• Southern east coast: Thunderstorms 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, waves will reach one to two metres and about two metres offshore. From Nakhon Si Thammarat southwards, waves will be about one metre and one to two metres offshore. Waves may exceed two metres during thunderstorms.
• Southern west coast: Thunderstorms 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, waves will reach two to three metres and exceed three metres during thunderstorms. From Krabi southwards, waves will be about two metres and exceed two metres during thunderstorms.
• Bangkok and surrounding provinces: Thunderstorms across 70% of the area, with isolated heavy rain. Temperatures will range from 25-27°C to 31-34°C, with southwesterly winds of 10-25kph.

Rough seas prompt small-boat warning

Waves in the upper Andaman Sea are forecast to reach two to three metres and exceed three metres during thunderstorms.

The lower Andaman Sea and upper Gulf will have waves of about two metres, rising above two metres in stormy areas. All vessels in the Andaman Sea and Gulf of Thailand should proceed with caution and avoid thunderstorms, while small boats in the upper Andaman Sea should remain ashore.

Saudel strengthened from a tropical depression into a tropical storm over the upper South China Sea, east of Hainan Island. It is forecast to move close to Taiwan from September 3-4.

Travellers heading towards Taiwan have been advised to check the latest weather conditions before departure. The TMD stressed that the storm is not forecast to enter Thailand.

The advisory was signed by TMD director-general Sugunyanee Yavinchan. The department will issue its next update at 5pm on Tuesday.

Weather information is available around the clock through the TMD’s telephone numbers 0-2399-4012-13 and 1182.