Thai Met warns 35 provinces heavy rain

Thailand’s Meteorological Department issued a series of weather advisories on May 15 and May 16 warning of heavy to very heavy rain across parts of the country as the southwest monsoon strengthened over the Andaman Sea, Thailand and the Gulf. The agency said people in affected areas should watch for flash floods and overflows, especially near foothills, waterways and low-lying areas. The warnings also covered rough seas in the upper Andaman Sea, where waves were forecast at 2 to 3 meters and above 3 meters in thundershowers. ### Which Thai agency issued the warning, and when? The Thai Meteorological Department said in Warning No. 6, dated May 15, 2026, that the southwest monsoon would strengthen and bring more rain nationwide, with isolated heavy to very heavy rain in the North, Central, East and South. The advisory said the warning took effect at 5 p.m. local time on May 15 and named Sugunyanee Yavinchan, the department’s director-general, as signatory. (tmd.go.th) The department’s home page showed Warning No. 7 dated May 16, 2026, carrying the same headline on heavy to very heavy rain and strong wind-waves in the upper Andaman Sea. That indicates the warning remained in force into May 16, the date referenced in local coverage of 35 provinces facing heavy rain. ### What hazards did the department spell out? The May 15 advisory said heavy rain and accumulated rainfall could trigger flash floods and overflows, particularly along foothills, near waterways and in lowlands. (tmd.go.th) The department used similar language again in its May 17 daily forecast, warning people to beware of heavy rain accumulation in those same types of areas. (tmd.go.th) Marine conditions were a second focus. The department said waves in the upper Andaman Sea from Phuket northward were expected at 2 to 3 meters, with heights above 3 meters in thundershowers, while the lower Andaman Sea from Krabi southward and the upper Gulf were expected at about 2 meters and above 2 meters in thundershowers. It told all ships to proceed with caution and said small boats in the upper Andaman Sea should remain ashore. (tmd.go.th) ### Where was the rain expected to be heaviest? The department’s warning described the risk in regional terms rather than, in the material publicly visible here, listing all 35 provinces by name. It said isolated heavy to very heavy rain was expected in the North, Central, East and South. Local reporting by The Thaiger said 35 provinces were covered, including Andaman-side coastal areas, but the official advisory available through the department’s English-language pages summarized the threat by region. (tmd.go.th) The May 17 daily forecast gave province-level examples of heavy-rain risk, naming Chiang Rai, Phayao, Nan, Tak, Kamphaeng Phet and Phetchabun in the North; Nakhon Sawan, Uthai Thani, Kanchanaburi, Ratchaburi, Nakhon Pathom and Samut Sakhon in the Central region; and Chanthaburi and Trat in the East. The same forecast said rain would be concentrated mostly in the western part of the country. (tmd.go.th) ### Why did conditions worsen this weekend? The department said an active low-pressure cell in the lower Bay of Bengal was moving toward the upper Bay of Bengal while the southwest monsoon over the Andaman Sea, Thailand and the Gulf strengthened. That combination, according to the agency, was expected to increase rainfall and roughen seas during May 14-18. (tmd.go.th) The May 17 forecast said the southwest monsoon remained strong over the Andaman Sea, the South and the Gulf, producing continuous rainfall in Thailand. The seven-day forecast also said heavy to very heavy rain would persist in the upper country during May 16-22, with an active low-pressure cell expected over Myanmar and western Thailand during May 17-22. ### What should readers watch next? (tmd.go.th) The department’s daily forecast dated May 17 said stronger monsoon conditions were still bringing continuous rain, isolated heavy falls and rough seas, especially in western areas and the upper Andaman Sea. The agency’s seven-day outlook extended the period of heavy to very heavy rain through May 22 in parts of the country. Thailand’s next official updates are expected through the Meteorological Department’s warning and daily forecast pages, where the agency has been issuing numbered advisories and day-by-day regional forecasts as conditions evolve. (tmd.go.th 1) (tmd.go.th 2)