"Meteorological Department" (Thailand's Meteorological Department) Second announcement warning for Upper Thailand from 18-21 August 2026 "Heavy to very heavy rain" May cause flash floods and flash floods from mountain runoff
16 August 2026Meteorological DepartmentAnnouncement regarding "Heavy to very heavy rain in Upper Thailand" Effective from 18 to 21 August 2026, second announcement states that during this period, Thailand will experience heavy to very heavy rain in some areas, especially in the North and Northeast regions. This is due to a monsoon trough passing over the North and Upper Northeast, combined with a fairly strong southwest monsoon covering the Andaman Sea, Thailand, and the Gulf of Thailand.
Residents in these areas are advised to be cautious of the dangers from heavy to very heavy rain and accumulated rainfall, which may cause flash floods and flash floods from mountain runoff, especially in foothill areas near waterways and lowlands. They should avoid traveling through frequently flooded routes, particularly in low-lying areas where short-term flooding may occur.
Regarding sea conditions, the upper Andaman Sea will experience fairly strong winds from 19 to 21 August 2026, with waves 2-3 meters high, and over 3 meters in areas with thunderstorms. The lower Andaman Sea and upper Gulf of Thailand will have waves about 2 meters high, with waves exceeding 2 meters where thunderstorms occur. Fishermen in the Andaman Sea and Gulf of Thailand are advised to navigate with caution and avoid sailing in stormy areas. Small boats in the upper Andaman Sea should refrain from leaving shore during these dates.
For safety and to minimize potential impacts, residents are urged to plan their activities and travel carefully during this period. They should follow announcements from the Meteorological Department and can access information at the Meteorological Department’s website http://www.tmd.go.th or by calling 0-2399-4012-13 and 1182, available 24 hours.