TMD issues heavy rain warning for central and southern Thailand
Heavy to very heavy rain may cause flash floods, while Andaman waves could exceed three metres in thundershowers and small boats should remain ashore.
- The Thai Meteorological Department has issued a warning for heavy to very heavy rain in central and southern Thailand, effective from September 18 to 20.
- The weather is caused by a monsoon trough moving south across the central and upper southern regions, intensified by a strong southwesterly monsoon over the Andaman Sea.
- Residents are warned of potential flash floods and run-off, particularly in low-lying areas and on slopes near waterways.
- The warning includes strong winds and waves of 2-3 meters in the Andaman Sea, with an advisory for small boats to remain ashore until September 20.
The Thai Meteorological Department (TMD) issued Announcement No. 8 at 5pm on Friday (September 18, 2026), warning of heavy to very heavy rain across Thailand and strong winds and waves in the Andaman Sea. The announcement is effective from September 18 to 20.
During this period, parts of Thailand are forecast to receive heavy rain, with very heavy rain in some areas of the South.
A high-pressure system or cool air mass from China is expected to extend over the upper North and upper Northeast, causing the monsoon trough to move south across the Central, East and upper South.
A fairly strong southwesterly monsoon will also prevail over the Andaman Sea, Thailand and the Gulf of Thailand.
“People across Thailand should beware of heavy to very heavy rain and accumulated rainfall, which may cause flash floods and rapid run-off, particularly on slopes near waterways and in low-lying areas. Travel on routes prone to repeated flooding should be avoided, especially in low-lying areas, where temporary waterlogging may occur.”
Andaman Sea waves of 2-3 metres expected, with small boats advised to remain ashore through Sunday
Wind waves in the Andaman Sea will be fairly strong, reaching 2-3 metres and more than three metres in areas with thundershowers.
Mariners in the Gulf of Thailand and the Andaman Sea should navigate with caution and avoid areas with thundershowers.
Small boats in the Andaman Sea should remain ashore from September 18 to 20.
To improve safety and reduce possible impacts, people are advised to plan their daily activities and journeys carefully during the period and monitor announcements from the TMD.
Updates are available at tmd.go.th or by calling 0-2399-4012-13 and 1182, 24 hours a day.
Thailand weather forecast from 6pm on Friday (September 18) to 6pm on Saturday (September 19)
North
- Thundershowers are forecast across 70% of the region, with isolated heavy rain in Mae Hong Son, Chiang Mai, Lamphun, Lampang, Phrae, Tak, Sukhothai, Kamphaeng Phet, Phichit, Uttaradit, Phitsanulok and Phetchabun.
- Temperatures will range from 23-27 degrees Celsius to 30-36 degrees Celsius, with easterly winds of 10-20 km/h.
Northeast
- Thundershowers are forecast across 60% of the region, with isolated heavy rain in Maha Sarakham, Roi Et, Loei, Nong Bua Lam Phu, Chaiyaphum, Khon Kaen, Nakhon Ratchasima and Buriram.
- Temperatures will range from 23-25 degrees Celsius to 31-34 degrees Celsius, with easterly winds of 10-20 km/h.
Central
- Thundershowers are forecast across 80% of the region, with isolated heavy rain in Nakhon Sawan, Uthai Thani, Chai Nat, Lopburi, Saraburi, Sing Buri, Ang Thong, Phra Nakhon Si Ayutthaya, Suphan Buri, Kanchanaburi, Ratchaburi, Nakhon Pathom, Samut Songkhram and Samut Sakhon.
- Temperatures will range from 23-25 degrees Celsius to 34-35 degrees Celsius, with variable winds of 10-25 km/h.
East
- Thundershowers are forecast across 70% of the region, with isolated heavy rain in Chachoengsao, Chonburi, Rayong, Nakhon Nayok, Prachinburi, Sa Kaeo, Chanthaburi and Trat.
- Temperatures will range from 23-27 degrees Celsius to 32-34 degrees Celsius, with southwesterly winds of 20-35 km/h. Waves will be about two metres high and more than two metres in areas with thundershowers.
South (east coast)
- Thundershowers are forecast across 60% of the region, with isolated heavy rain in Phetchaburi, Prachuap Khiri Khan, Chumphon, Surat Thani, Nakhon Si Thammarat, Phatthalung and Songkhla. Temperatures will range from 23-26 degrees Celsius to 30-34 degrees Celsius.
- From Surat Thani northwards, southwesterly winds will reach 20-35 km/h. Waves will be 1-2 metres high, about two metres offshore and more than two metres in areas with thundershowers.
- From Nakhon Si Thammarat southwards, southwesterly winds will reach 15-35 km/h. Waves will be about one metre high, rising to 1-2 metres offshore and more than two metres in areas with thundershowers.
South (west coast)
- Thundershowers are forecast across 80% of the region, with isolated heavy rain in Trang and Satun and very heavy rain in some areas of Ranong, Phang Nga, Phuket and Krabi. Temperatures will range from 23-25 degrees Celsius to 27-31 degrees Celsius.
- From Phuket northwards, southwesterly winds will reach 20-40 km/h. Waves will be 2-3 metres high and more than three metres in areas with thundershowers.
- From Krabi southwards, southwesterly winds will reach 20-35 km/h. Waves will be about two metres high and more than two metres in areas with thundershowers.
Bangkok and surrounding provinces
- Thundershowers are forecast across 80% of the area, with isolated heavy rain.
- Temperatures will range from 24-26 degrees Celsius to 31-34 degrees Celsius, with southwesterly winds of 10-25 km/h.
