Weathermen warn of unseasonal cold and windy weather in the upper part of the country until next Tuesday, while heavy rain is forecast for parts of the South.
The Meteorological Department said on Thursday that temperatures would drop 2-4°C but rain would decline in the North, the Northeast, the Central Plains and the East due to a high pressure system from China, that would also increase winds in the region.
Meanwhile, heavy rain was possible in some areas in the South, including its eastern coast, due to easterly winds in the Gulf of Thailand.
The temperature fell to 9°C on the peak of Doi Inthanon mountain in the northern province Chiang Mai on Thursday morning.
Thanawut Panjaporn-udomlap, meteorological director for the North, said the high pressure system from China caused the cold weather, which was unseasonal as the country had not entered winter yet.
Temperatures on low-lying areas of Chiang Mai as well as adjacent Chiang Rai and Mae Hong Son provinces fell to 20-22°C, he said.
In the northeastern province of Kalasin, morning temperatures dropped to 18-19°C. Provincial governor Kraisorn Kongchalard advised people to wear winter jackets.