Thailand is experiencing sharply contrasting weather patterns as a cold air mass blankets upper regions of the country while heavy rainfall and rough seas persist in the lower South amid an active northeast monsoon.

Meteorologists reported that a high-pressure system originating over China has extended over northern, northeastern and central areas, pushing temperatures down and bringing cool to cold conditions, particularly in the early mornings.

In some northern provinces and at higher elevations, temperatures have dipped to around fourteen degrees Celsius, and frost has been observed on mountain peaks, prompting health advisories for residents and travellers to dress warmly. 

Meanwhile, the lower South, including provinces such as Phatthalung, Songkhla, Pattani, Yala and Narathiwat, is contending with heavy to very heavy rainfall as the northeast monsoon strengthens over the Gulf of Thailand and the Andaman Sea.

Weather forecasts warn of potential flash floods and water runoff in foothill regions and low-lying areas, urging local communities to remain vigilant.

Mariners have also been cautioned as sea conditions deteriorate, with waves around the lower Gulf reaching one-to-two metres and rising above two metres in areas affected by thunderstorms, increasing the risk for small craft at sea. 

Coastal and offshore areas across the Gulf of Thailand and the Andaman Sea are expected to see ongoing unsettled conditions, with winds and seas complicating navigation and fishing activities.

The combined effects of the cold air mass and monsoon moisture have created starkly different experiences across the country, with cool, brisk mornings in the upper regions contrasting with intense downpours and hazardous marine conditions in the southern provinces.

Authorities have advised the public to take appropriate precautions, including preparing for colder weather up north and monitoring flood warnings and sea advisories in the South as the weather system continues to evolve.