Results of the oscillations analysis of the Belarussian Polesia lakes temperature regime are presented. Data of long-term instrumental observations of the water temperature for two unique Belarussian Polesia lakes are used, that is Vygonoshanskoe and Chervonoe. Differentiated computational interval is accepted, with monthly discretisation from May to October and decade discretisation for April and November. Maximum water temperature was reviewed separately. Water temperature dynamics in lakes has complex and ambiguous nature. Water temperature shows most clear growth in August and September at Vygonoshanskoe and in July, August, September and October at Chervonoe. Maximum water temperature growth is observed in July and August at Chervonoe, and it is higher than 0,7 °C in 10 years. Statistically-significant growth of maximum water temperatures is not observed, but growth tendencies are present. Speed of these processess is sub- stanitally different per territory. It is caused by specifics of temperature and wind structure, formed on the Polessie territory in contemporary conditions.