The Meteorological Department issued Warning No. 11 for heavy to very heavy rain in upper Thailand, listing provinces to prepare for flash floods and mountain runoff, with impacts lasting until 21 Aug 2026.
20 August 2026 GMT+7 Meteorological Department Announcement on Heavy to Very Heavy Rain in Upper Thailand (Effective until 21 August 2026) Issue No. 11
It states that parts of Thailand are experiencing heavy to very heavy rain, especially in the northern and northeastern regions, due to a monsoon trough passing over northern and upper northeastern Thailand 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 dangers from heavy to very heavy rain and accumulated rainfall, which may cause flash floods and mountain runoff, particularly in foothill areas near waterways and low-lying areas. They should avoid traveling through frequently flooded routes, especially in low-lying zones where short-term flooding may occur.
Waves and winds in the upper Andaman Sea and upper Gulf of Thailand are fairly strong, with waves 2-3 meters high; areas with thunderstorms may see waves over 3 meters. The lower Andaman Sea has waves about 2 meters high, exceeding 2 meters where thunderstorms occur. Mariners in these seas should navigate cautiously and avoid sailing in thunderstorm areas. Small boats in the upper Andaman Sea and upper Gulf of Thailand are advised not to leave shore during these days.
For safety and to minimize potential impacts, the public is urged to plan their activities and travel cautiously during this period and to follow announcements from the Meteorological Department. Updated information is available on the Meteorological Department's website.https://www.tmd.go.thor by calling 0-2399-4012-13 and hotline 1182, available 24 hours.
20 August 2026 GMT+7
21 August 2026 GMT+7
