Lakes are important parts of land water resources, and their surface water temperatures are the most sensitive and rapid response to climate and environmental changes. An accurate understanding of their changing characteristics is highly important for analysing and understanding global climate change and improving the ecological environment of lakes. In July 2022, the Meteorological Observation Centre of China Meteorological Administration and the National Satellite Meteorological Centre jointly deploy drift buoys at the China Radiometric Calibration Site of remote sensing satellite (CRCS) to carry out the Fengyun Satellite “lake-sea” cooperative observation experiment. Two sets of drift buoys are deployed on the line from Haixin Mountain to the southeast of Lake Qinghai. In this paper, we use data from the drift buoy from 10 July to 30 September, 2022, combined with data from four sets of automatic meteorological stations on the land around Lake Qinghai, to analyse the characteristics and correlations between the changes of water temperature and air temperature in Lake Qinghai, and the differences in the characteristics of the changes of air temperature on the lake and land. To ensure the reasonableness of the test data, quality control of the test data is conducted, including spatial consistency checks, climatological threshold checks and temporal consistency checks, and a total of 13488 sets of water temperature data and 20232 sets of air temperature data are screened out. The analysis results of the above data indicate that there is a certain correlation between water temperature and air temperature in Lake Qinghai, the correlation coefficient of the minute value is 0.71, and the correlation coefficient of the daily mean value is 0.73. The diurnal variations of water temperature and air temperature are unimodal, and the rising and falling stages are basically the same; however, the diurnal variations of water temperature are obviously smaller than those of air temperature, and the decreasing time is earlier than that of air temperature. The diurnal variations in lake and land air temperatures exhibit a certain off-peak phenomenon, the peak land air temperature is advanced, and the valley value is lagging. The factors influencing the correlation between air and water temperatures are diverse and are related not only to subsurface characteristics and the distance from the observation location but also to solar and surface radiation. The contributions of multisource observational data, such as total radiation, shortwave radiation, cloud remote sensing products and high-resolution satellite observations, to the difference between air and water temperatures are analysed during the day and night and in different seasons in future work. The study of the difference between air and water temperatures can provide technical support for analysing heat exchanges between the lake and the atmosphere of Lake Qinghai.