Measurements of solar radiation fluxes were taken with minute discreteness from March 27 to April 6, 2020 in the subglacial layer of Lake Vendyurskoe and in the water column of Lake Golubaya Lamba at 0–2.9 m depths. Seasonal surveys using the RBRConcerto probe in the vertical sounding mode were carried out in these lakes and in Lake Rindozero in early summer (June) and in autumn (October). When the ice was 40 cm thick and the snow was 1–2 cm thick, the solar radiation flux in the under-ice layer of Lake Vendyurskoe reached 90–100 W/m2, and when snow covered the surface, it sharply decreased to almost zero. With the same ice and snow thickness, the flux of photosynthetic active solar radiation (PAR) reached 360–410 μmol/(m2·s) in the under-ice layer of Golubaya Lamba. For Golubaya Lamba, the values of the extinction coefficients averaged for 0–2.9 m depths were 0.47–0.57 m-1 during the spring under-ice period; the depth of 1 % irradiation (photic zone) calculated from these values was 3.2–6.7 m, meaning it can reached the bottom on some sunny days. In June 2020, PAR fluxes in the surface layer of Lake Vendyurskoe (depth 0.5 m) reached 1000 μmol/(m2·s), decreasing to zero below 4 m depth. In Golubaya Lamba, the PAR flux reached 150 μmol/(m2·s) at a depth of 4 m in summer, and 50 μmol/(m2·s) during the ice-covered period and in autumn. In Lake Rindozero, the PAR flux rapidly decreased with depth and was practically zero below 2 m in June and October 2020. The values of the extinction coefficients for the open water period varied within 0.99–1.97 m-1 in Lake Vendyurskoe, 1.60–1.88 m-1 in Lake Rindozero, 0.12–0.14 m-1 in Golubaya Lamba.