Continuous rainfall is forecast for the whole country with isolated heavy rains in the lower North, the Northeast, the Central, the East and the South regions.
People should beware of rain accumulation that may cause flash floods, the department said.
The weather forecast for the next 24 hours:
North: Thundershowers in 60 per cent of the areas with isolated heavy rains; temperature lows of 23-25 degrees Celsius, highs of 32-35°C.
Northeast: Thundershowers in 70 per cent of the areas with isolated heavy rains; temperature lows of 23-25°C, highs of 31-33°C.
Central: Thundershowers in 70 per cent of the areas with isolated heavy rains; temperature lows of 23-25°C, highs of 32-34°C.
East: Thundershowers in 70 per cent of the areas with isolated heavy to very heavy rains; temperature lows of 23-25°C, highs of 32-33°C; waves a metre high and 1-2 metres during thundershowers.
South (east coast): Thundershowers in 60 per cent of the areas with isolated heavy rains; temperature lows of 23-25°C, highs of 32-33°C; waves a metre high and 1-2 metres during thundershowers.
South (west coast): Thundershowers in 70 per cent of the areas with isolated heavy rains; temperature lows of 20-24°C, highs of 29-31°C; waves 1-2 metres high and two metres during thundershowers.
Bangkok and surrounding areas: Thundershowers in 70 per cent of the areas with isolated heavy rains; temperature lows of 24-25°C, highs of 32-34°C.