Northern Thailand faces heavy rain as monsoon trough crosses region

SUNDAY, AUGUST 16, 2026
Northern Thailand faces heavy rain as monsoon trough crosses region

Thailand’s Meteorological Department warns of heavy rain in the North, flash flood risks and rough seas in the Andaman Sea, with storms across 40% of Bangkok.

  • Heavy rain and thunderstorms are forecast across 60% of northern Thailand due to a monsoon trough crossing the region.
  • The severe weather is caused by the monsoon trough combined with a strong southwest monsoon over the Andaman Sea and the Gulf of Thailand.
  • Residents in northern provinces, particularly Mae Hong Son, Tak, and Phetchabun, are warned of potential flash floods and overflowing rivers.
  • People in affected areas are advised to be cautious of accumulated rainfall, especially in low-lying areas near foothills and waterways.

The Thai Meteorological Department (TMD) has warned of heavy rain in parts of northern Thailand on Sunday (August 16), with thunderstorms forecast across 60% of the region. Bangkok and surrounding areas are expected to see thunderstorms across 40% of the area.

The department’s 24-hour forecast showed that heavy rain would persist in some parts of the North, upper Northeast, East and the west coast of the South.

The conditions are being driven by a monsoon trough extending across Myanmar, upper northern Thailand and upper Laos into a low-pressure area over upper Vietnam, combined with a rather strong southwest monsoon prevailing over the Andaman Sea, Thailand and the Gulf of Thailand.

People in affected areas have been advised to watch for heavy and accumulated rainfall that could trigger flash floods, rapid run-off and rivers overflowing their banks, particularly in low-lying areas and near foothills and waterways.

Conditions in the upper Andaman Sea remain relatively rough, with waves of 2-3 metres and more than 3 metres in areas affected by thunderstorms.

Mariners in the Andaman Sea and the Gulf of Thailand should proceed with caution and avoid sailing in areas affected by thunderstorms, while small boats in the upper Andaman Sea should remain ashore for the time being.

Regional weather forecast through Monday morning

The forecast covers the period from 6am on Sunday to 6am on Monday.

  • North: Thunderstorms are forecast across 60% of the region, with heavy rain in some areas, particularly Mae Hong Son, Tak and Phetchabun. Temperatures will range from lows of 22-27°C to highs of 32-36°C.
     
  • Northeast: Thunderstorms are expected across 40% of the region, with isolated heavy rain in Bueng Kan, Sakon Nakhon and Nakhon Phanom. Temperatures will range from 24-26°C to 33-35°C.
     
  • Central: Thunderstorms are forecast across 40% of the region, mainly in Nakhon Sawan, Lop Buri, Saraburi and Kanchanaburi. Temperatures will range from 23-27°C to 33-35°C.
     
  • East: Thunderstorms are expected across 40% of the region, with heavy rain in some areas of Chanthaburi and Trat. Temperatures will range from 24-28°C to 30-34°C.
     
  • South (east coast): Thunderstorms are forecast across 40% of the region, mainly in Prachuap Khiri Khan, Chumphon, Surat Thani and Nakhon Si Thammarat. Temperatures will range from 23-26°C to 33-36°C.
     
  • South (west coast): Thunderstorms are expected across 60% of the region, with heavy rain in some areas of Ranong and Phang Nga. Temperatures will range from 24-27°C to 30-33°C.
     
  • Bangkok and surrounding areas: Thunderstorms are forecast across 40% of the area. Temperatures will range from lows of 26-28°C to highs of 33-35°C.