TMD warns heavy rain across Thailand as 39 provinces face flood risks

The Thai Meteorological Department (TMD) has warned that heavy to very heavy rain will continue across many parts of Thailand until Thursday (May 21), raising concerns over flash floods, forest run-off and dangerous sea conditions.

In its latest weather advisory, the department said 39 provinces remained at risk from persistent rainfall, particularly areas along foothills, waterways and low-lying ground.

The warning covers several regions nationwide, with the highest concern focused on the South’s west coast, the East and parts of the lower North.

Forecasters said the situation was being driven by a fairly strong southwesterly monsoon covering the upper Andaman Sea and Thailand, although the system has begun to weaken gradually. A low-pressure cell over the North and upper Vietnam is also contributing to unstable weather conditions.

The TMD said rainfall in some areas had started to ease, but isolated heavy rain was still expected across western parts of the country, the eastern region and the upper Northeast, while very heavy rain remained possible along the South’s west coast.

Residents in risk-prone areas were advised to remain alert for sudden flooding and run-off, especially near mountain slopes and natural waterways where accumulated rainfall could quickly trigger dangerous conditions.

Rough seas and strong winds continue

The department also warned of strong waves in the Andaman Sea and parts of the Gulf of Thailand.

From Phuket northwards, waves in the upper Andaman Sea are forecast at 2-3 metres, rising above 3 metres during thunderstorms.

In the lower Andaman Sea, from Krabi southwards, and in the upper Gulf, waves are expected at around 2 metres, with higher seas in stormy areas.

The TMD urged all vessels to proceed with caution and avoid thunderstorm zones, while small boats in the upper Andaman Sea were advised to remain ashore during the warning period.

Rain bands spotted near Bangkok region

The department also reported scattered rain clusters moving across Pathum Thani, Nakhon Nayok and Ayutthaya provinces on Thursday afternoon before shifting northeastward.

Forecasters expected rain to continue covering parts of Nakhon Nayok for more than one hour during the late afternoon period.

Regional forecast

North

Thunderstorms are forecast across 60% of the region, with heavy rain expected in Mae Hong Son, Chiang Mai, Nan, Uttaradit, Sukhothai, Tak, Kamphaeng Phet, Phichit, Phitsanulok and Phetchabun.

Northeast

Thunderstorms are expected across 40% of the region, with heavy rain forecast in Loei, Nong Khai, Bueng Kan, Nong Bua Lamphu, Udon Thani, Sakon Nakhon, Nakhon Phanom and Nakhon Ratchasima.

Central region

Thunderstorms are forecast across 60% of the region, with heavy rain likely in Nakhon Sawan, Uthai Thani, Lop Buri, Kanchanaburi and Ratchaburi.

East

Thunderstorms are forecast across 60% of the region, particularly in Rayong, Chanthaburi and Trat, where heavy rain is expected.

South (east coast)

Thunderstorms are forecast across 60% of the area, with heavy rain expected in Phetchaburi, Prachuap Khiri Khan, Chumphon, Surat Thani, Nakhon Si Thammarat and Phatthalung.

South (west coast)

Thunderstorms are expected across 70% of the region, with heavy rain forecast in Phuket, Krabi, Trang and Satun, while Ranong and Phang Nga face the risk of very heavy rainfall.

Bangkok and surrounding areas

Thunderstorms are forecast across 60% of the capital and nearby provinces, with isolated heavy rain possible and temperatures reaching up to 37°C.