Isolated heavy rain is likely in the North, the Northeast and the East. People in these areas should beware of the severe conditions, the department said.
The department also said a category 2 tropical depression is moving west, expected to develop into a category 3 tropical storm before making landfall over Guangdong, China during August 19-20.
The weather forecast for the next 24 hours is as follows:
North: Cloudy with thundershowers in 60 per cent of the areas and isolated heavy rains; temperature lows of 23-24 degrees Celsius and highs of 29-34°C.
Northeast: Cloudy with thundershowers in 70 per cent of the areas and isolated heavy rains; temperature lows of 22-25°C and highs of 26-34°C.
Central: Cloudy with thundershowers in 60 per cent of the areas; temperature lows of 23-26°C, highs of 33-35°C.
East: Cloudy with thundershowers in 60 per cent of the areas and isolated heavy rains; temperature lows of 23-27°C, highs of 31-34°C; waves a metre high and 1-2 metres during thundershowers.
South (east coast): Mostly cloudy with thundershowers in 30 per cent of the areas; temperature lows of 23-25°C, highs of 32-35°C; waves a metre high and 1-2 metres during thundershowers.
South (west coast): Partly cloudy with thundershowers in 20 per cent of the areas; temperature lows of 23-25°C, highs of 33-34°C; waves a metre high and two metres during thundershowers.
Bangkok and surrounding areas: Cloudy with thundershowers in 60 per cent of the areas; temperature lows of 25-26°C, highs of 33-35°C.