The Thai Meteorological Department has warned of unsettled weather as the south-west monsoon continues to prevail, bringing heavy rain to 48 provinces across Thailand, including Bangkok. Some areas are at risk of forest run-off and flash floods, especially low-lying areas, while boat operators are advised to beware of strong waves.
On June 20, 2026, the Thai Meteorological Department forecast that over the next 24 hours, the East, Bangkok and surrounding provinces, and the lower South would see heavy rain in some areas.
This is due to a moderate south-west monsoon still prevailing over the Andaman Sea, Thailand and the Gulf of Thailand, combined with a low-pressure cell covering upper Vietnam.
People in the affected areas are advised to prepare for heavy rain and accumulated rainfall, which could trigger flash floods and forest run-off, especially in risk areas near waterways and low-lying zones.
Waves in the upper Andaman Sea are moderate at 1-2 metres high. In the lower Andaman Sea and the Gulf of Thailand, waves are about one metre high. In thunderstorm areas, waves may rise above two metres.
Boat operators in the Andaman Sea and the Gulf of Thailand are advised to navigate with caution and avoid sailing in thunderstorm areas.
