With a strong high-pressure area covering upper Thailand and the South China Sea, the temperature will drop by 3-5 degree Celcius in the northern and central parts of the country - including Bangkok and its vicinity - during Dec 17-18, the Thai Meteorological Department said in its 11am announcement on Sunday.
Mountaintops will be very cold with isolated frost.
During Dec 19-21, another strong high-pressure area from China will reach upper Thailand. As a result, cold spells will continue and the temperature will decrease further by 2-3 degree Celcius.
In the South, more rain and the rough seas are expected Dec 17-18. Waves will be 2-3 metres high in the lower Gulf of Thailand, with the possibility of onshore surges. During Dec 19-21, there will be less rain, but waves in the Gulf are forecast to be 2-4 metres high.
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