New Year weather: cool spell ends before countdown, heavy rain risk in the South
The Thai Meteorological Department says upper Thailand will cool and turn windy on December 26-28, before temperatures rise slightly on December 29-January 1, while the South sees heavy rain and high waves in the Gulf.
The Thai Meteorological Department (TMD) has issued its New Year weather outlook for December 26, 2025 to January 1, 2026, warning that the cool spell in upper Thailand is expected to ease before the New Year countdown, while the South faces periods of heavy rain and rough seas.
December 26-28, 2025
Upper Thailand will see falling temperatures and stronger winds. The Northeast and North are expected to be cool to cold, with temperatures in the North and Central regions dropping by 2-4°C.
In the Northeast, the East, and Bangkok and surrounding areas, temperatures are forecast to fall by 1-3°C, as a fairly strong high-pressure system, or cold air mass from China, spreads over upper Thailand and the South China Sea.
The South will see heavy to very heavy rain in some areas, driven by a relatively strong northeast monsoon covering the Gulf of Thailand, the South and the Andaman Sea.
Sea conditions are expected to be rough at times:
- Lower Gulf of Thailand: waves 2-3 metres, rising above 3 metres in thunderstorms
- Upper Gulf of Thailand: waves around 2 metres, rising above 2 metres in thunderstorms
December 29, 2025-January 1, 2026
Temperatures in upper Thailand are expected to edge up, though conditions will remain cool to cold, with light morning fog, as the high-pressure system weakens. Upper-level northwesterly winds will continue to prevail.
In the lower South, rainfall should decrease, though heavy rain may still occur in some places, as the northeast monsoon weakens.
Waves are expected to ease slightly:
- Lower Gulf of Thailand: around 2 metres, and about 2 metres in thunderstorms
- Upper Gulf of Thailand: 1-2 metres, around 2 metres in thunderstorms
