Heavy rain risk shifts towards Bangkok and southern Thailand

Bangkok and surrounding provinces face a risk of very heavy rain on September 10–11, with Thailand’s latest weather warning covering heavy downpours and potential flooding through September 13.

In warning No. 6, the Thai Meteorological Department (TMD) forecast heavy to very heavy rain in parts of the North, Northeast, Central region and East on Wednesday (September 9, 2026).

From September 10–13, continuing rain is expected across the lower Northeast, Central region, including Bangkok and surrounding provinces, the East and the South. Some locations could experience heavy to very heavy downpours, while rainfall is expected to decrease in the North and upper Northeast.

Monsoon trough moves south

A high-pressure system, or cool air mass, extending into northern Vietnam and northern Laos has pushed the monsoon trough across northern Thailand, the upper Central region and the Northeast. A moderate southwest monsoon is also covering the Andaman Sea, Thailand and the Gulf of Thailand.

During September 10–13, the high-pressure system from China is expected to extend over the upper North and upper Northeast. This will push the monsoon trough further south, across the lower Central region, lower Northeast and East, towards a strong low-pressure area in the central South China Sea. The southwest monsoon over the Andaman Sea, southern Thailand and the Gulf will strengthen.

Areas at risk by date

The daily risk assessment from the TMD’s Weather Forecast Division identifies the following provinces and areas. Red denotes a risk of very heavy rain, while orange denotes heavy rain.

September 9

Very heavy rain — red

• North: Phitsanulok and Phetchabun.
• Northeast: Loei, Nong Bua Lam Phu, Chaiyaphum and Khon Kaen.

Heavy rain — orange

• North: Mae Hong Son, Chiang Mai, Chiang Rai, Phayao, Nan, Sukhothai, Uttaradit, Tak, Kamphaeng Phet and Phichit.
• Northeast: Nong Khai, Bueng Kan, Udon Thani, Sakon Nakhon, Nakhon Phanom, Kalasin, Mukdahan, Maha Sarakham, Roi Et, Yasothon, Amnat Charoen, Nakhon Ratchasima, Buri Ram, Surin, Si Sa Ket and Ubon Ratchathani.
• Central: Nakhon Sawan, Ayutthaya, Lop Buri, Saraburi, Nakhon Pathom and Samut Sakhon, including Bangkok and surrounding provinces.
• East: Nakhon Nayok, Prachin Buri, Sa Kaeo, Chachoengsao, Chanthaburi and Trat.
• South: Ranong and Phang Nga.

September 10

Very heavy rain — red

• North: Tak and Kamphaeng Phet.
• Northeast: Nakhon Ratchasima and Buri Ram.
• Central: Nakhon Sawan and Ayutthaya, including Bangkok and surrounding provinces.
• East: Nakhon Nayok, Chanthaburi and Trat.

Heavy rain — orange

• North: Mae Hong Son, Chiang Mai, Chiang Rai, Phayao, Lamphun, Lampang, Phrae, Sukhothai, Uttaradit, Phichit, Phitsanulok and Phetchabun.
• Northeast: Chaiyaphum, Khon Kaen, Surin, Si Sa Ket and Ubon Ratchathani.
• Central: Chai Nat, Lop Buri, Saraburi, Sing Buri, Ang Thong, Suphan Buri, Kanchanaburi, Ratchaburi, Nakhon Pathom, Samut Sakhon and Samut Songkhram.
• East: Prachin Buri, Sa Kaeo, Chachoengsao, Chon Buri and Rayong.
• South: Ranong, Phang Nga, Phuket, Krabi, Phetchaburi, Prachuap Khiri Khan, Chumphon and Surat Thani.

September 11

Very heavy rain — red

• Central: Uthai Thani, Kanchanaburi, Ratchaburi, Nakhon Pathom, Samut Songkhram and Samut Sakhon, including Bangkok and surrounding provinces.
• East: Rayong, Chanthaburi and Trat.
• South: Phetchaburi, Prachuap Khiri Khan, Chumphon, Ranong and Phang Nga.

Heavy rain — orange

• North: Tak, Kamphaeng Phet, Phichit and Phetchabun.
• Northeast: Khon Kaen, Maha Sarakham, Roi Et, Chaiyaphum, Nakhon Ratchasima, Buri Ram, Surin, Si Sa Ket and Ubon Ratchathani.
• Central: Nakhon Sawan, Chai Nat, Lop Buri, Saraburi, Sing Buri, Ang Thong, Ayutthaya and Suphan Buri.
• East: Nakhon Nayok, Prachin Buri, Sa Kaeo, Chachoengsao and Chon Buri.
• South: Surat Thani, Phuket, Krabi, Trang and Satun.

September 12, 2026

Very heavy rain — red

• Central: Uthai Thani, Suphan Buri, Saraburi and Kanchanaburi.
• East: Chanthaburi and Trat.

Heavy rain — orange

• North: Mae Hong Son, Chiang Mai, Lamphun, Uttaradit, Sukhothai, Kamphaeng Phet, Phichit, Phetchabun and Tak.
• Northeast: Khon Kaen, Maha Sarakham, Roi Et, Yasothon, Amnat Charoen, Chaiyaphum, Nakhon Ratchasima, Buri Ram, Surin, Si Sa Ket and Ubon Ratchathani.
• Central: Nakhon Sawan, Chai Nat, Lop Buri, Sing Buri, Ang Thong, Ayutthaya, Ratchaburi, Nakhon Pathom, Samut Songkhram and Samut Sakhon, as well as Bangkok and surrounding provinces.
• East: Nakhon Nayok, Prachin Buri, Sa Kaeo, Chachoengsao, Chon Buri and Rayong.
• South: Phetchaburi, Prachuap Khiri Khan, Chumphon, Surat Thani, Ranong, Phang Nga and Phuket.

September 13

Very heavy rain — red

• Central: Kanchanaburi, Uthai Thani, Suphan Buri, Ratchaburi, Nakhon Pathom, Samut Songkhram and Samut Sakhon.
• East: Chachoengsao, Chon Buri, Rayong, Chanthaburi and Trat.
• South: Ranong and Phang Nga.

Heavy rain — orange

• North: Tak and Kamphaeng Phet.
• Northeast: Nakhon Ratchasima, Buri Ram, Surin, Si Sa Ket and Ubon Ratchathani.
• Central: Nakhon Sawan, Chai Nat, Lop Buri, Saraburi, Sing Buri, Ang Thong and Ayutthaya, including Bangkok and surrounding provinces.
• East: Nakhon Nayok, Prachin Buri and Sa Kaeo.
• South: Phetchaburi, Prachuap Khiri Khan, Chumphon, Surat Thani, Narathiwat, Phuket and Krabi.

South China Sea system could strengthen

The TMD is also monitoring a strong low-pressure area over the central South China Sea that is likely to develop into a tropical cyclone during September 11–13. The system is expected to approach the coast of northern Vietnam on September 14–15.

Its subsequent development could affect Thailand’s weather. The department urged the public to follow forecasts closely as the system develops.

Flash-flood and travel warnings

Heavy downpours and accumulated rainfall could trigger flash floods and rapid runoff, particularly on foothill slopes near waterways. Low-lying areas and urban districts with slow drainage could experience short-term flooding.

Motorists should avoid routes prone to repeated flooding and roads covered by deep water. Residents in the affected areas should monitor weather warnings and take account of the conditions when planning journeys.

Weather information is available around the clock through the TMD website, the 1182 hotline, and telephone numbers 02-399-4012 and 02-399-4013.