Heavy rain and possible flooding is likely in many northern and northeastern provinces from Thursday to Saturday as Tropical Storm Dianmu, now over the South China Sea, approaches northern Vietnam.
Wanchai Sakudomchai, head of the Meterological Department, said on Thursday the tropical storm, which had just developed from a depression, was covering the Gulf of Tonkin and would enter northern Vietnam on Friday and then move on to Laos.
That would bring increasing rain to upper Thailand, with heavy downpours and runoff possible in some areas.
A flood warning was issued for the northeastern provinces of Bung Kan, Loei, Nakhon Phanom, Nong Bua Lam Phu, Nong Khai, Sakon Nakhon, Ubon Ratchathani and Udon Thani on Thursday and Friday.
Similar conditions were possible in the northern provinces of Chiang Mai, Chiang Rai, Lampang, Lamphun, Mae Hong Son, Nan, Phayao, Phetchabun, Phitsanulok, Phrae, Tak and Uttaradit on Friday and Saturday.
Small boats should remain ashore until Sunday.