BANGKOK — Thailand’s Meteorological Department has issued a fresh warning for heavy to very heavy rainfall across several parts of the country on September, with authorities cautioning residents about possible flash floods and rapidly rising water levels.

The warning is linked to a high-pressure system extending from China toward northern Thailand, while the monsoon trough has shifted southward across parts of the North, Northeast and Central regions. An active low-pressure system is also located over the central South China Sea.

The weather agency said continuous rainfall and isolated heavy showers are expected across the country. Areas of the western North, lower Northeast, Central Thailand, Bangkok and surrounding areas, and the East could experience heavy to very heavy rain.

The southwest monsoon is also affecting the Andaman Sea, southern Thailand, the Central region, the East and the Gulf of Thailand. These combined weather systems are contributing to unsettled conditions across large parts of the country.

The meteorological department warned that intense rainfall could produce sudden runoff and flash flooding, particularly in low-lying areas, near waterways and in locations vulnerable to accumulated rainwater.

Residents in affected areas are being advised to monitor official weather updates and remain alert to rapidly changing conditions. People living near hills, streams and other flood-prone locations should take additional precautions.

The warning is particularly relevant to Bangkok and surrounding communities because heavy rainfall can place pressure on urban drainage systems and cause temporary flooding on roads and in residential areas.

Thailand’s weather authorities said the current advisory is effective on September 10, with another update scheduled later the same day.

The latest warning highlights the continuing influence of monsoon conditions over Thailand and the importance of early preparation as rainfall intensity can vary considerably between regions.