Cold surge chills upper Thailand; monsoon brings heavy Southern rain

The Thai Meteorological Department (TMD) has warned on Friday (December 26) that a new wave of cold air from China is spreading across upper Thailand, bringing a sharp temperature drop and stronger winds.

The North and Northeast will feel wintry conditions, with lows around 13°C.

The South, meanwhile, faces rough conditions as a strengthening monsoon hits 10 provinces, raising the risk of flooding and flash floods.

Mariners are advised to stay ashore.

The TMD forecast that over the next 24 hours, the lower South would see more rain, with heavy to very heavy downpours in some areas, especially Surat Thani, Nakhon Si Thammarat, Phatthalung, Songkhla, Pattani, Yala and Narathiwat.

This is due to a stronger northeast monsoon covering the Gulf of Thailand, the South and the Andaman Sea.

Residents in the lower South are urged to watch for heavy to very heavy rain and accumulated rainfall that could trigger flash floods and run-off, particularly on foothills near waterways and in low-lying areas.

Winds and waves in the lower Gulf remain fairly strong, with waves of 2–3 metres, and above 3 metres in thunderstorms.

The upper Gulf will see waves around 2 metres, rising above 2 metres in thunderstorms.

Boaters in both the Gulf of Thailand and the Andaman Sea should proceed with caution and avoid sailing in thunderstorm areas.

Small boats in the lower Gulf should remain ashore until December 28, 2025.

Upper Thailand will see falling temperatures and stronger winds as another fairly strong high-pressure system, or cold air mass, from China spreads over the region.

People in upper Thailand are advised to take care of their health as temperatures turn colder, and to be alert to fire hazards due to dry, windy conditions.

Dust levels during this period: the Central region, including Bangkok and surrounding areas, will see moderate to fairly high dust/haze accumulation due to poor ventilation.

Other regions will remain in the good to moderate range.

Thailand forecast from 6am Friday (December 26) to 6am Saturday (December 27)

Northern Region

• Cool to cold with morning fog; temperatures to fall by 1–3°C.
• Low: 14–20°C
• High: 27–32°C
• Mountaintops: cold to very cold; frost in some places.
• Low: 3–12°C
• Northeast wind 10–25 km/h.

Northeastern Region

• Cool to cold in the morning with strong winds; temperatures to fall by 1–2°C.
• Low: 13–19°C
• High: 27–31°C
• Mountaintops: cold.
• Low: 8–14°C
• Northeast wind 15–30 km/h.

Central Region

• Cool in the morning with strong winds; temperatures to fall by 1–3°C.
• Low: 17–21°C
• High: 30–32°C
• Northeast wind 10–30 km/h.

Eastern Region

• Cool in the morning with strong winds; temperatures to fall by 1–3°C.
• Low: 18–23°C
• High: 30–33°C
• Northeast wind 15–35 km/h.
• Sea: waves around 1 metre; about 2 metres offshore.

Southern Region (East Coast)

• Thunderstorms in 60% of the area, with heavy to very heavy rain in some places, especially Surat Thani, Nakhon Si Thammarat, Phatthalung, Songkhla, Pattani, Yala and Narathiwat.
• Low: 20–23°C
• High: 28–31°C
• From Surat Thani northwards: northeast wind 20–35 km/h; sea waves around 2 metres, above 2 metres in thunderstorms.
• From Nakhon Si Thammarat southwards: northeast wind 20–40 km/h; sea waves 2–3 metres, above 3 metres in thunderstorms.

Southern Region (West Coast)

• Thunderstorms in 40% of the area, with heavy rain in some places, especially Krabi, Trang and Satun.
• Low: 22–24°C
• High: 30–32°C
• Northeast wind 15–35 km/h.
• Sea: waves around 1 metre; 1–2 metres offshore; above 2 metres in thunderstorms.

Bangkok and the surrounding areas

• Cool in the morning with strong winds; temperatures to fall by 1–2°C.
• Low: 21–23°C
• High: 30–33°C
• Northeast wind 10–30 km/h.