TMD forecasts heavy rain in 41 provinces over 24 hours

The Thai Meteorological Department (TMD) forecast heavy rain in 41 provinces, including isolated very heavy downpours in parts of the North, Central region and East. Thunderstorms were expected across 70% of Bangkok and surrounding areas, with heavy rain in some locations.

The TMD expected rainfall to decrease elsewhere, although isolated heavy downpours remained possible. Accumulated rainfall could continue to cause flooding even where rainfall eased.

Western and lower North face heavy to very heavy rain

The TMD identified the western and lower North, western Central region and East as areas where heavy to very heavy rain remained possible. Residents, particularly in the North, Central region and East, were warned of flash floods, prolonged flooding, overflowing rivers, sudden runoff and landslides.

The TMD highlighted foothill areas near waterways and low-lying locations as particularly vulnerable. Travellers were advised to avoid routes prone to flooding, especially low-lying roads where water could temporarily accumulate.

The TMD’s weather outlook attributed the conditions to a low-pressure area that had moved into the Gulf of Martaban, while a fairly strong south-westerly monsoon continued to cover the Andaman Sea, southern
Thailand and the Gulf of Thailand

Upper Andaman Sea and upper Gulf face waves of 2–3 metres

The TMD forecast waves of 2–3 metres in the upper Andaman Sea and upper Gulf of Thailand, exceeding 3 metres during thunderstorms. Mariners across the Andaman Sea and Gulf were advised to proceed cautiously and avoid areas experiencing thunderstorms.

The TMD’s small-boat advisory called for vessels in the upper Andaman Sea and upper Gulf to remain ashore until September 28, 2026.

Regional forecasts put Bangkok thunderstorm coverage at 70%

The TMD’s regional outlook covers a 24-hour period from 6am to 6am the following day. Thunderstorms are forecast across 70% of Bangkok and surrounding areas, with the regional details as follows:

North: Thunderstorms across 70% of the region, with isolated heavy rain in Chiang Rai, Lamphun, Lampang, Phrae, Sukhothai, Kamphaeng Phet and Phetchabun. Isolated very heavy rain is forecast in Mae Hong Son, Chiang Mai and Tak. Temperatures: Minimum 23–25°C; maximum 28–34°C. Winds: Easterly at 10–20km/h.

Northeast: Thunderstorms across 60% of the region, with isolated heavy rain in Loei, Chaiyaphum, Nakhon Ratchasima and Buri Ram. Temperatures: Minimum 23–24°C; maximum 28–32°C. Winds: Easterly at 10–25km/h.

Central region: Thunderstorms across 70% of the region, with isolated heavy rain in Chai Nat, Lop Buri, Saraburi, Sing Buri, Ang Thong, Phra Nakhon Si Ayutthaya, Nakhon Pathom, Samut Sakhon and Samut Songkhram. Isolated very heavy rain is forecast in Nakhon Sawan, Uthai Thani, Suphan Buri, Kanchanaburi and Ratchaburi. Temperatures: Minimum 22–24°C; maximum 27–30°C. Winds: Variable at 10–25km/h.

East: Thunderstorms across 70% of the region, with isolated heavy rain in Sa Kaeo and Chachoengsao. Isolated very heavy rain is forecast in Nakhon Nayok, Prachin Buri, Chon Buri, Rayong, Chanthaburi and Trat. Temperatures: Minimum 22–24°C; maximum 26–30°C. Winds: South-westerly at 20–40km/h. Waves: 2–3 metres, exceeding 3 metres during thunderstorms.

South, east coast: Thunderstorms across 60% of the region, with isolated heavy rain in Phetchaburi and Prachuap Khiri Khan. Temperatures: Minimum 21–25°C; maximum 29–34°C. From Surat Thani northwards:

South-westerly winds at 20–35km/h, with waves around 2 metres and exceeding 3 metres during thunderstorms. From Nakhon Si Thammarat southwards: South-westerly winds at 15–35km/h, with waves of 1–2 metres and exceeding 3 metres during thunderstorms.

South, west coast: Thunderstorms across 60% of the region, with isolated heavy rain in Ranong, Phang Nga and Phuket. Temperatures: Minimum 23–25°C; maximum 29–34°C. From Ranong northwards: South-westerly winds at 20–40km/h, with waves of 2–3 metres and exceeding 3 metres during thunderstorms. From Phang Nga southwards: South-westerly winds at 15–35km/h, with waves of 1–2 metres and exceeding 2 metres during thunderstorms.

Bangkok and surrounding areas: Thunderstorms across 70% of the area, with isolated heavy rain. Temperatures: Minimum 23–25°C; maximum 28–31°C. Winds: Southerly at 10–25km/h.