
The downpours are the result of a strong monsoon trough lying across the North and the upper Northeast converging with the low-pressure cell over the Gulf of Tonkin.
Meanwhile, the moderate southwest monsoon prevailing over the Andaman Sea, the Central, the East, the South and the Gulf will bring isolated thundershowers to these areas.
The department advised people to beware of rain accumulation that may cause flash floods and overflows, especially along foothills near waterways and lowlands. Road users should also take more caution during thundershowers.
For sea conditions, waves in the upper Andaman Sea and the upper Gulf are about 2 metres high and higher in thundershowers. The lower Andaman Sea and the lower Gulf, however, will experience calmer seas with wave height of about 1-2 metres.
All ships in the upper Andaman Sea and the upper Gulf should proceed with caution and keep away from storms, the department warned.
The department also mentioned that the latest East Pacific tropical storm Yun-Yeung is expected to move toward the eastern part of Japan on Friday and Saturday. This storm has no effect on Thailand.