Thermal and dissolved oxygen dynamics in a small ice-covered lake Vendyurskoe (South Karelia) are considered on the basis of the data analysis carried out within the three-year field survey conducted with stand-alone precision equipment. Using FFT analysis we identified the main periods of variability of the temperature, dissolved oxygen and the pressure ranged from several minutes to 1–12 days. Seiches, presumably arising from the impact of wind on the ice and the change in atmospheric pressure over the lake, advective transport, caused by uneven heating of sediments and bathymetric features of the lake basin, as well as spring under-ice convective mixing play an important role in the dynamics of an ice-covered lake.