The department forecast that from June 16-18, the southwest monsoon will weaken while the monsoon trough will shift across Myanmar and upper Laos.
During the period, less rain with isolated thundershowers are likely mostly in western Thailand.
However, from June 19 to 21, the southwest monsoon will strengthen and the monsoon trough will move down from across Myanmar and upper Laos. More rains are then likely in western Thailand along with isolated heavy showers in the North, the upper Northeast, the East and the South. During the period, people in upper Thailand should beware of severe conditions that may cause flash floods and overflows, the department said, adding that all transport should proceed with extra caution.
Additionally, the Bangkok Metropolitan Administration (BMA) said that until June 20, the Chao Phraya River level at Phra Chulachomklao Fort in Samut Prakan province will rise to 1.7 to 2 metres due to high tide from 6pm to 3am.
The BMA advised people who live near the river in Bangkok and Samut Prakan to move their belongings to higher places and follow weather updates regularly via http://dds.bangkok.go.th
Here’s the weather forecast for June 16-21:
North: Thundershowers in 20-40 per cent of the area during June 16-18, and 40-60 per cent of the area with gusty winds and isolated heavy rains from June 19 to 21; temperature lows of 22-26 degrees and highs of 31-37 degrees Celsius.
Northeast: Thundershowers in 20-40 per cent of the areas June 16-18, and 40-60 per cent of the area with gusty winds and isolated heavy rains June 19-21; temperature lows of 23-26 degrees and highs of 32-37 degrees Celsius.
Central: Thundershowers in 20-40 per cent of the area; temperature lows of 22-27 degrees, highs of 33-37 degrees Celsius.
East: Thundershowers in 20-40 per cent of the areas June 16-18, and 40-60 per cent of the area with isolated heavy rains June 19-21; temperature lows of 23-28 degrees and highs of 30-36 degrees Celsius; waves 1-2 metres high and 2 metres during thundershowers.
South (east coast): Thundershowers in 40-60 per cent of the area with isolated heavy rains; temperature lows of 23-27 degrees, highs of 30-36 degrees Celsius; waves 1-2 metres high and 2 metres during thundershowers.
South (west coast): Thundershowers in 40-60 per cent of the area with isolated heavy rains; temperature lows of 23-28 degrees, highs of 30-34 degrees Celsius; waves 1-2 metres high and 2 metres during thundershowers.
Bangkok and surrounding areas: Thundershowers in 20-40 per cent of the area June 16-18, and 40-60 per cent of the area with isolated heavy rains June 19-21; temperature lows of 25-28 degrees and highs of 31-37 degrees Celsius.