Thailand: Heavy Rain Expected from September 23 to 27, Bangkok and Coastal Areas Affected
Written by the editors of theo-courant.com, your reference guide to Thailand and South-East Asia - based in Bangkok, at the heart of Thai culture.
Heavy rain is expected across several parts of Thailand from September 23 to 27, 2026. Bangkok and its surrounding areas are among those affected, while rougher sea conditions are expected in the Gulf of Thailand.
Key points: forecast for September 24 to 27
- September 23–27*: Heavy rain is expected across several regions of Thailand.
- Bangkok: Heavy showers are possible, with isolated periods of very heavy rain from September 23 to 27.
- Gulf of Thailand: Waves of 2 to 3 metres are expected, with higher waves during thunderstorms.
- Small boats in the upper Gulf: The TMD recommends that small vessels remain ashore.
- The forecast mainly covers the North, lower Northeast, Central Thailand, East and South.
Heavy rain expected across several regions
The Thai Meteorological Department (TMD) forecasts heavy rain across several parts of Thailand from September 23 to 27, with isolated periods of very heavy rain.
The weather deterioration will begin in the lower Northeast and East before extending to other regions. The North, Central Thailand, Bangkok and its surrounding areas, the East and the South are all included in the current forecast. The TMD attributes the change to a low-pressure area moving from central Vietnam, combined with strengthening southwesterly monsoon conditions.
The weather department is also warning about water accumulation, which could lead to rapid runoff and flash flooding in some low-lying areas and locations near waterways.
Bangkok particularly affected from September 24
Showers and thunderstorms are expected in Bangkok and its surrounding areas throughout the period. The TMD is forecasting isolated periods of very heavy rain from September 24 to 27.
This does not mean that Bangkok is expected to experience widespread flooding. However, the weather conditions could temporarily lead to water accumulation in areas that are particularly vulnerable during periods of heavy rain.
For travellers in Bangkok, journeys may become more difficult during the heaviest downpours, particularly on roads prone to water accumulation.
Rougher sea conditions expected
The weather deterioration will also affect coastal and maritime areas.
In the upper Gulf of Thailand, waves are expected to reach 2 to 3 metres, with waves exceeding 3 metres during thunderstorms. The TMD recommends that small vessels remain ashore from September 23 to 27.
Along the Andaman coast, waves could reach around 2 metres in several areas and become higher during thunderstorms. Vessels are advised to exercise caution and avoid areas affected by thunderstorms.
These conditions are particularly relevant for boat trips and other maritime travel.
What does this mean for travellers in Thailand?
The period from *September 23 to 27 is expected to bring wetter conditions to several parts of Thailand, with Bangkok facing a particularly active period from September 24.
Travellers moving around the country during this period should monitor local weather updates and take road and sea conditions into account when heavy rain develops.
The TMD notes that forecasts may change as the low-pressure area moves. Checking the latest weather information before travelling is therefore advisable, particularly for boat journeys.
Sources: Thai Meteorological Department (TMD), weather forecasts and bulletins issued on September 21 and 22, 2026.
