The Meteorological Department issued Announcement No. 1 warning for the period 28 June to 3 July 2026. "Heavy to very heavy rain" across Thailand with possible flash floods and flash floods from mountain runoff.
On 26 June 2026, the Meteorological Department's website announced "Heavy to very heavy rain over Thailand and strong winds in the upper Andaman Sea (effective during 28 June to 3 July 2026)." Announcement No. 1 states that
from 28 June to 3 July 2026, rainfall will increase over Thailand with some areas experiencing heavy to very heavy rain, especially in the eastern region and the western side of the southern region. This is due to a monsoon trough passing over the north and upper northeastern regions, combined with the strengthening southwest monsoon blowing over the Andaman Sea, Thailand, and the Gulf of Thailand.
Residents in these areas are advised to be cautious of dangers from heavy to very heavy rain and accumulated rainfall, which may cause flash floods and flash floods from mountain runoff, particularly in foothill areas near waterways and low-lying basins.
Meanwhile, the upper Andaman Sea will experience fairly strong winds from 29 June to 3 July 2026, with waves 2–3 meters high; areas with thunderstorms may see waves higher than 3 meters.
The lower Andaman Sea and upper Gulf of Thailand will have waves about 2 meters high; areas with thunderstorms may see waves over 2 meters. Mariners in the Andaman Sea and Gulf of Thailand are urged to navigate cautiously and avoid sailing in areas experiencing thunderstorms. Small boats in the upper Andaman Sea should refrain from going out to sea during this period.
For safety and to minimize possible impacts, the public is advised to carefully plan their activities and travel during this time. Please follow updates from the Meteorological Department, available on their website http://www.tmd.go.th or by calling 0-2399-4012-13 and 1182, available 24 hours a day.