Thailand warns 14 southern provinces of heavy rain and floods

Thailand’s water authorities have warned 14 southern provinces to prepare for heavy rain, flash floods, runoff and river overflows from October 26-29 as the monsoon trough strengthens over the region.

The Office of the National Water Resources (ONWR) issued its 12th warning of 2026 covering Chumphon, Ranong, Phang Nga, Phuket, Krabi, Surat Thani, Nakhon Si Thammarat, Trang, Satun, Phatthalung, Songkhla, Yala, Pattani and Narathiwat.

The agency said a cold air mass from China would extend over upper Thailand and the South China Sea, while easterly winds would carry moisture from the South China Sea and the Gulf of Thailand over upper Thailand and the upper South.

At the same time, the monsoon trough over southern Thailand is expected to strengthen, bringing persistent rain with heavy to very heavy falls in some areas.

Phuket records 128mm of rain

ONWR’s water situation report at 7am on Monday (October 26) showed Phuket recorded the highest rainfall in the South at 128 millimetres.

The highest regional totals elsewhere were 90mm in Phrae, 74mm in Khon Kaen, 41mm in Pathum Thani, 57mm in Trat and 57mm in Ratchaburi.

Rainfall is forecast to ease in much of Thailand from October 29-31, although parts of the eastern coast of the South are still expected to experience heavy rain.

Reservoirs and major rivers under watch

ONWR has called for close monitoring of Rajjaprabha Dam in Surat Thani, where water storage exceeds 80% of capacity, as well as medium-sized and small reservoirs holding more than 80% across the 14 southern provinces.

Authorities have also been told to monitor water levels in major rivers and waterways, including:

• Chumphon Canal and the Lang Suan River in Chumphon
• Tapi and Phum Duang rivers in Surat Thani
• Takua Pa River in Phang Nga
• Cha-uat and Tha Di canals in Nakhon Si Thammarat
• Palian Canal and Trang River in Trang
• La-ngu and Duson canals in Satun
• Tha Nae Canal in Phatthalung
• Pattani and Sai Buri rivers
• Kolok River and Tanyong Mat Canal in Narathiwat

Reservoirs nationwide at 83% of capacity

As of October 25, reservoirs across Thailand held a combined 66.76 billion cubic metres of water, equivalent to 83% of total storage capacity.

Usable water amounted to 42.63 billion cubic metres, or 75%.

Reservoirs in the western region were at 97% of capacity, while those in the East were at 90%.

Among the major dams in the Chao Phraya basin, Bhumibol Dam was at 71% of capacity, Sirikit Dam at 82%, Kwae Noi Bamrung Daen Dam at 86% and Pa Sak Jolasid Dam at 93%.

Agencies told to prepare for rapid flooding

ONWR instructed relevant agencies to closely monitor rainfall and water conditions, particularly in areas receiving more than 90mm of accumulated rain within 24 hours and locations with a history of repeated flooding.

Officials were also told to inspect and repair river embankments, clear drainage obstructions and drains, and coordinate water-discharge plans from upstream to downstream while taking tidal conditions into account.

Authorities should prepare personnel and equipment for emergency assistance and provide advance warnings so residents in at-risk areas have enough time to evacuate if necessary.