ONWR warns high tides could affect seven provinces in Thailand
The warning covers Monday (June 15, 2026) to Thursday (June 18, 2026), with low-lying riverside communities urged to prepare for overflow and saltwater intrusion.
- Thailand's Office of the National Water Resources (ONWR) has issued a high-tide warning for seven provinces from June 15-18, 2026.
- The high tides, driven by a strong southwest monsoon, are expected to cause major rivers like the Chao Phraya to overflow into low-lying areas.
- The seven at-risk provinces include Bangkok, Samut Prakan, and Nonthaburi, with potential flooding on major roads and saltwater intrusion affecting water supplies.
The Office of the National Water Resources (ONWR) has issued an announcement warning relevant agencies and the public to closely monitor high-tide conditions from Monday (June 15, 2026) to Thursday (June 18, 2026), as they may cause water levels in major rivers to overflow into low-lying areas and communities without protective barriers.
Cause explained: “strong monsoon” pushes up high tides
Monitoring of weather conditions has found that the influence of a fairly strong south-west monsoon covering the Andaman Sea, southern Thailand and the Gulf of Thailand is a key factor causing water levels at river mouths connected to the sea to rise significantly.
Seven at-risk provinces and three major roads under watch
ONWR said water may flow into and inundate low-lying areas along the Chao Phraya River, Mae Klong River and Tha Chin River, as well as communities outside flood embankments and areas without permanent flood defences.
The seven at-risk provinces are:
- Bangkok
- Samut Prakan
- Nonthaburi
- Pathum Thani
- Samut Sakhon
- Nakhon Pathom
- Samut Songkhram
Routes at risk of standing floodwater: motorists and other road users are urged to exercise extra caution on major roads, including Sukhumvit Road, Suksawat Road and Rama II Road, where water may overflow onto road surfaces during the period.
Farmers and the public are warned over “saltwater intrusion” affecting drinking and domestic water
Apart from flooding concerns, another condition requiring strict vigilance is saltwater intrusion into main waterways, which would directly affect the quality of water used for consumption and domestic purposes, as well as riverside agricultural areas that could be damaged by salinity levels exceeding standard limits.
ONWR is therefore asking local agencies to prepare machinery and equipment and quickly issue public warnings to people in at-risk areas so they can prepare and minimise possible impacts as far as possible.
