Global warming has led to significant changes in the thermodynamic characteristics of lakes on the Tibetan Plateau, resulting in a vital impact on the lake ecosystem and water quality changes. In this study, continuous observations of lake water temperature and meteorological conditions were carried out in the largest lake—Selin Co, Tibet. The characteristics of the intra-annual thermodynamic of Selin Co and its response to meteorological conditions are revealed. Results from water temperature profile monitoring between June 2021 and December 2022 indicate that Selin Co is a dimictic lake. Its thermodynamic regime can be divided into four phases: winter freezing, spring mixing, summer stratification and fall mixing. Selin Co starts to stratify during the freezing period (mid-March). The melting of the lake ice, the enhanced radiation penetrating the ice and the high salinity resulted in a rapid and stable stratification of the water column under the ice. However, complete mixing of the water column does not occur in spring, likely due to the persistent salinity gradients, and the mixing phenomenon was confined to the surface 0-30 m, with the bottom waters remaining slowly warmed. Schmidt stability values ranged from 0 to 520 J/m2 in Selin Co. From the characteristics of the thermocline, the daily variation patterns of the thermocline in 2021 and 2022 are very similar, with the maximum depth of the thermocline around 17 m during the summer stratification period. Wind speed and solar radiation have different driving mechanisms for thermal stratification during different periods. Wind and radiation contribute concurrently to thermal stratification during the formation period, and weakening radiation is the main cause of the disappearance of thermodynamic stratification. Comparative analysis showed that air temperature changes were more variable than surface water temperature, which lagged air temperature by about 21 days. This study conducted the first continuous observation and analysis of the thermodynamic characteristics of Selin Co and its driving factors, providing a scientific basis for an in-depth understanding of water temperature dynamics in inland lakes on the Tibetan Plateau and their response to regional climate change, as well as lake modelling research.