The temperature of standing water is one of the most frequently measured abiotic parameters of lakes. While some of the Tatra lakes have been investigated in modern times, those in the Karkonosze Mountains have never been an object of planned, systematic thermal studies. Our article presents the results of a unique methodology of research on the thermal characteristics of waters of Wielki Staw and Morskie Oko. They yielded full information about the vertical distribution of water temperatures in both lakes in an exceptionally warm month - July 2006. By employing gradient thermal probes, it was possible not only to give a general description of the thermal conditions of the lakes and the current development of stratification, but also to grasp the pattern of momentary fluctuations in the water temperatures of both lakes. The research has proved that the thermal conditions of the two mountain lakes largely result from their individual morphometric diversity. Also, in terms of thermal characteristics, the lakes should not be treated on a par with those of the other geographical regions of Poland; in favourable circumstances, the temperatures of their surface waters can reach values rarely met even among lowland lakes.