Heavy rain forecast for 21 provinces as monsoon strengthens

Bangkok, 14 August 2026 - Heavy rainfall will persist across 21 provinces in Thailand over the next day, with some regions experiencing particularly intense downpours, the Meteorological Department warns. A monsoon trough stretching across Myanmar, upper Laos and upper Vietnam, coupled with a robust southwesterly monsoon over the Andaman Sea and the Gulf of Thailand, is driving the heavy rainfall.

Authorities urge residents to remain vigilant for potential flash floods, landslides and overflow of rivers in low-lying areas, especially in foothills, near waterways. Wind speeds and wave heights in the upper Andaman Sea will escalate to 2-3 meters, rising above 3 meters in areas hit by thunderstorms, necessitating caution from boat operators and small vessels in the area.

Forecast for the next 24 hours indicates thunderstorms covering 60% of the northern region, with isolated heavy rain in Mae Hong Son, Nan and Tak, while temperatures range from 22-35°C. Similar patterns are expected in the central region, with 40% of the area under thunderstorms and isolated heavy rain in Saraburi, Kanchanaburi, Udon Thani, Nong Khai and surrounding areas.

Winds will be 10-35km/h, and waves will be 2 meters or higher during thunderstorms. Coastal regions from Chumphon to Phuket will also experience similar conditions, with varying wind speeds and wave heights. Bangkok and its surrounding provinces will see 60% of the area under thunderstorms, isolated heavy rain and temperatures between 26-34°C.