The Meteorological Department forecast is for temperatures to fall by 2-8°C in northern and upper southern areas, with heavy rain expected in the lower South, from Wednesday through to Monday next week.
Director-general Kanrawee Sitthicheewapak, director-general of the department, said on Monday that a cold spell from China would extend into Thailand and the South China Sea during the period.
As a result, temperatures would drop by an expected 5-8°C in the Northeast, 4-6°C in the North, 3-5°C in the Central Plain and the East and 2-4°C in the upper South, she said.
Meanwhile, northeast monsoon winds will be stronger in the Gulf of Thailand and the South and a low pressure system from the South China Sea will pass the lower Gulf of Thailand and Malaysia.
Consequently, it will rain heavily in the lower South, Ms Kanrawee said. She warned people in the region of possible risk from runoff and flash floods.