Monthly Weather Summary

In August 2025, the weather was dominated by the southwest monsoon, which prevailed over the Andaman Sea, Thailand, and the Gulf of Thailand throughout the month and it was weak at the beginning of the month resulted in less rainfall in Thailand at that time. After that, from the middle and at the end of the month, rainfall was relatively increased in many areas, both amount and distribution of rain, primarily in the northern, northeastern, eastern coastal areas, and the southern west coast. In addition, the monsoon trough occasionally lay across the northern and northeastern regions and shifted further north to lie over Myanmar, upper Laos and upper Vietnam at times. Moreover, the southwest monsoon which prevailing over the Andaman Sea, Thailand, and the Gulf of Thailand was strengthened during this period. Besides, Thailand was also affected by the remnant of tropical cyclones including typhoon “KAJIKI, (2513)” made landfall at Vinh, Vietnam, on 25 August. It subsequently weakened into a tropical storm and then a tropical depression over Laos, before further weakening into an active low-pressure cell covering northern Thailand during 26-27 August accompanied with the tropical storm “NONGFA, (2514)” made landfall at Ha Tinh, Vietnam, on 30 August. It weakened into a tropical depression over Laos, and then into an active low-pressure cell over Nakhon Phanom province, and covering Nong Khai, Loei, and lower northern Thailand in the following days. These conditions brought increasing in rainfall in many areas, particularly in the northern and northeastern regions, where abundant rain with heavy to very heavy rainfall was reported at the end of the month, inducing flooding in several areas, as well as flash floods and landslides in some places. In the southern region, scanty rain was found at the beginning of the month due to the weak southwest monsoon. After that, rainfall relatively increased, particularly along the west coast. However, the total rainfall in August was near or below-normal rainfall in most regions, including the northern part 4.8 mm (2%), northeastern part 25.6 mm (9%), central part 54.2 mm (29%), southern part (east coast) 2.9 mm (2%), and southern part (west coast) 29.1 mm (7%) and it was above-normal in the eastern part 30.6 mm (1%). The average total rainfall over Thailand in August was 5% below normal. Overall, the average temperature in Thailand was 0.5°C above normal. For moredetails are as follows.