ONWR warns 15 provinces across Thailand of heavy rain and flood risk
Rainfall may exceed 100mm within 12 hours in parts of Thailand between Friday (May 29, 2026) and Monday (June 1, 2026), with Phuket under close watch.
- Thailand's Office of the National Water Resources (ONWR) has warned 15 provinces of heavy rain and potential flooding from May 29 to June 1, 2026.
- The warning is due to a strong south-west monsoon, with rainfall potentially exceeding 100mm in 12 hours, creating risks of flash floods and forest run-off.
- The affected provinces are located in the Northern, Eastern, Western, and Southern regions of the country.
- Phuket is highlighted as a specific area of concern due to its limited capacity to handle large volumes of rain, which could lead to significant standing floodwater.
The Office of the National Water Resources (ONWR) has warned people in 15 provinces nationwide to monitor continuing accumulated heavy rainfall, which may exceed 100 millimetres within 12 hours from Friday (May 29, 2026) to Monday (June 1, 2026), creating a risk of flash floods, forest run-off and flooding in community areas, especially in Phuket, where there are constraints on handling large volumes of rain.
Latest monitoring and assessment of the water situation found that Thailand remains under the influence of a fairly strong south-west monsoon prevailing over the Andaman Sea, Thailand and the Gulf of Thailand, together with a monsoon trough across upper Thailand.
As a result, rainfall has increased in many areas, with heavy to very heavy rain in some places.
Based on its latest data analysis, the ONWR said several areas require special monitoring because accumulated rainfall may exceed 100 millimetres within 12 hours, namely:
- Northern region: Mae Hong Son, Chiang Mai and Tak
- Eastern region: Rayong, Chanthaburi and Trat
- Western region: Kanchanaburi, Ratchaburi, Phetchaburi and Prachuap Khiri Khan
- Southern region: Chumphon, Ranong, Phang Nga, Phuket and Krabi
The ONWR therefore asked people in at-risk areas to monitor the situation closely and exercise extra caution, especially in low-lying areas in urban communities that often experience flooding when drainage cannot keep up, as well as areas at risk of flash floods and forest run-off.
Phuket is another area requiring close monitoring because of constraints on its capacity to cope with large accumulated rainfall, which could cause standing floodwater to accumulate and affect travel for people in many areas.
