TMD forecasts widespread rain in 45 provinces and Bangkok

The Thai Meteorological Department (TMD) has forecast increased rainfall across Thailand on Friday (September 4, 2026), with isolated heavy rain and very heavy falls possible in the upper North and eastern Northeast.

The regional forecast names 45 provinces and lists Bangkok separately.

Heavy rain is explicitly forecast in 38 provinces, while seven provinces on the southern east coast are identified as the main areas for thunderstorms.

The 24-hour forecast runs from 6am on Friday to 6am on Saturday (September 5).

A monsoon trough has moved southwards across the North and upper Northeast before extending into a low-pressure area over the Gulf of Tonkin.

A moderate southwest monsoon is also prevailing over the Andaman Sea, Thailand and the Gulf of Thailand.

Flood and marine precautions

The TMD warned that heavy and accumulated rainfall could trigger flash floods and rapid run-off, particularly in the Mekong River basin, on foothills near waterways and in low-lying areas.

People should avoid routes that regularly flood, especially low-lying roads where temporary waterlogging could develop quickly.

Sea conditions in the Andaman Sea and Gulf of Thailand are moderate.

Waves in the upper Andaman Sea will be about two metres high and exceed two metres during thunderstorms.

Mariners should proceed cautiously and avoid sailing in areas affected by thunderstorms.

Regional forecast from 6am Friday

North

• Thunderstorms across 60% of the region.
• Heavy rain in Mae Hong Son, Chiang Mai, Lamphun, Lampang, Phrae, Uttaradit, Tak, Phitsanulok, Phetchabun, Chiang Rai, Phayao and Nan.
• Minimum temperatures of 22-27°C.
• Maximum temperatures of 31-35°C.
• Southwesterly winds of 10-20 kilometres per hour.

Northeast

• Thunderstorms across 70% of the region.
• Heavy rain in Loei, Nong Bua Lamphu, Udon Thani, Nong Khai, Sakon Nakhon, Kalasin, Khon Kaen, Maha Sarakham, Roi Et, Si Sa Ket, Bueng Kan, Nakhon Phanom, Mukdahan, Yasothon, Amnat Charoen and Ubon Ratchathani.
• Minimum temperatures of 23-26°C.
• Maximum temperatures of 32-34°C.
• Southwesterly winds of 10-20 kilometres per hour.

Central region

• Thunderstorms across 60% of the region.
• Heavy rain in Lop Buri and Saraburi.
• Minimum temperatures of 25-27°C.
• Maximum temperatures of 34-36°C.
• Southwesterly winds of 10-20 kilometres per hour.

East

• Thunderstorms across 60% of the region.
• Heavy rain in Nakhon Nayok, Chanthaburi and Trat.
• Minimum temperatures of 23-27°C.
• Maximum temperatures of 31-35°C.
• Southwesterly winds of 15-35 kilometres per hour.
• Waves of one to two metres, rising above two metres during thunderstorms.

South on the east coast

• Thunderstorms across 40% of the region, mainly in Surat Thani, Nakhon Si Thammarat, Phatthalung, Songkhla, Pattani, Yala and Narathiwat.
• Minimum temperatures of 23-26°C.
• Maximum temperatures of 33-35°C.
• Southwesterly winds of 15-35 kilometres per hour.
• Waves of about one metre, rising to one to two metres offshore and above two metres during thunderstorms.

South on the west coast

• Thunderstorms across 60% of the region.
• Heavy rain in Phang Nga, Phuket, Krabi, Trang and Satun.
• Minimum temperatures of 23-25°C.
• Maximum temperatures of 31-33°C.
• From Phuket northwards, southwesterly winds of 20-35 kilometres per hour.
• From Phuket northwards, waves of about two metres, rising above two metres during thunderstorms.
• From Krabi southwards, southwesterly winds of 15-35 kilometres per hour.
• From Krabi southwards, waves of one to two metres, rising above two metres during thunderstorms.

Bangkok and surrounding provinces

• Thunderstorms across 60% of the area.
• Minimum temperatures of 26-27°C.
• Maximum temperatures of 33-35°C.
• Southwesterly winds of 10-25 kilometres per hour.
• Saudel weakens over Guangdong

The TMD said Depression Saudel over Guangdong province in China had weakened into an active low-pressure area.