The Meteorological Department has issued its 5th warning. "Heavy to very heavy rainfall". Across upper Thailand, check provinces at risk of impact; be alert for flash floods and mountain runoff.
On 17 August 2026, the websiteof the Meteorological Departmentissued a statement on heavy to very heavy rainfall in upper Thailand (effective 18-21 August 2026), 5th edition (159/2569).
It stated that from 18 to 21 August 2026, Thailand will experience heavy to very heavy rainfall in some areas, especially in the northern and northeastern 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. People in these areas should be cautious of heavy and accumulated rainfall that may cause flash floods and mountain runoff, particularly in foothill areas near waterways and lowlands. Travelers should avoid routes prone to repeated flooding, especially low-lying areas where short-term flooding may occur.
Waves in the upper Andaman Sea will be fairly strong from 19 to 21 August 2026, reaching heights of 2-3 meters, and over 3 meters in areas with thunderstorms. The lower Andaman Sea and upper Gulf of Thailand will have waves about 2 meters high, exceeding 2 meters during storms. Mariners in the Andaman Sea and Gulf of Thailand should navigate cautiously and avoid sailing in stormy areas. Small boats in the upper Andaman Sea are advised not to depart from shore during these dates for safety.
For safety and to minimize potential impacts, the public is advised to plan daily activities and travel with caution during this period. People should follow updates from the Meteorological Department and can access information on their website.http://www.tmd.go.thor call 0-2399-4012-13 and 1182, available 24 hours.
18 August 2026
19 August 2026
20 August 2026
21 August 2026
