Monthly Weather Summary

           In December 2025, the moderate to rather active high-pressure area covered upper Thailand almost the month. In addition, the westerly wind in the upper level occasionally prevailed over upper Thailand. These conditions caused cool weather in most of areas in the upper Thailand particularly cold weather occasionally was found in northern and northeastern parts. Regarding rainfall, it was generally scarce in upper Thailand except for rainfall was report mainly in northern part at the middle of the month, influenced by at the westerly trough occasionally moved through upper northern Thailand and upper Laos for few day. In contrast, the southern part of Thailand, influenced by at a moderate to rather active northeast monsoon over the Gulf of Thailand, southern part and the Andaman Sea almost the month and the presence of a low-pressure cell over the lower Gulf of Thailand and lower southern part during 11-13, experienced rainfall mainly along east coast almost the month. Overall, the average rainfall in Thailand for December was about 41% below normal levels. Specifically, northern part 6.0 mm (57%), central part 5.3 mm (67%), eastern part 7.2 mm (73%) southern part (east coast) 97.9 mm (37%) and southern part (west coast) 52.0 mm (57%). Interestingly, the northeastern part experienced above normal rainfall at 2.3 mm (47%). Temperature-wise, the average for the month was 0.6°C higher than normal. Further details are provided below.