A high-pressure system will see temperatures in the North, Central, East and Greater Bangkok drop by 3-5 degrees centigrade, said the department’s forecast.
The Northeast will experience an even bigger dip of 4-6C.
It advised people to look after their health during the sudden temperature change.
The department also warned of flash floods and overflows from heavy to very heavy rain in the South on Monday and Tuesday (December 11-12). Waves in the lower Gulf are expected to rise to two metres, and higher in thundershowers, it added. Boats in the lower Gulf should proceed with caution and keep off thundershowers.
Regional weather forecast for this week (Dec 12-17):
North: Mornings cool to cold with strong wind and 3-5C drop in temperature. Lows of 13-21C, highs of 29-32C. Temperature on hilltops likely to drop to 4-14C.
Northeast: Mornings cool to cold with strong wind and 4-6C drop in temperature. Lows of 13-20C and highs of 28-31C. Temperature on hilltops likely to drop to 8-14C.
Central: Mornings cool with strong wind and 3-5C drop in temperature. Lows of 16-22C and highs of 29-32C.
East: Mornings cool with strong wind and 3-5C drop in temperature. Lows of 17-22C and highs of 29-32C. Waves about 1 metre, 1-2 metres offshore.
South (east coast):
Monday: Scattered thundershowers and isolated heavy rain.
Tuesday-Saturday: Mornings cool in upper South. Isolated thundershowers in lower South.
Lows of 21-25C, highs of 26-33C.
Surat Thani upward: waves 1-2 metres and higher in thundershowers.
Nakhon Si Thammarat downward: Waves 2 metres and higher in thundershowers.
South (west coast):
Monday-Tuesday: Scattered thundershowers and isolated heavy rain.
Wednesday-Saturday: Isolated thundershowers.
Lows of 21-25C, highs of 26-33C. Waves 1-2 metre high and higher in thundershowers.
Greater Bangkok:
Monday-Saturday: Mornings cool with strong winds and 3-5C drop in temperature. Lows of 19-23C, highs of 29-33C.
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