It explained that a moderate high-pressure system from China is covering upper Thailand, bringing a reduction in temperatures coupled with strong winds especially in the Northeast.
Meanwhile, a monsoon trough is bringing heavy rains to some areas in the East and the South.
The department advised people in the area to beware of heavy showers and accumulated rain water that might cause flash floods.
It said winds in the Gulf of Thailand would cause 1-2-metre-high waves and more than 2 metres during thunderstorms.
Here’s the weather forecast until 6am on Thursday:
North
Northeast
Central
East
South (east coast)
South (west coast)
Bangkok and its vicinity