Trends of meteorological parameters potentially implicated in harmful algal blooms regularly occurring since early 2000-ies in a major Arctic freshwater basin the lake Imandra have been analyzed. Compared with the preceding period, increases occurred in mean annual and seasonal air temperatures, sunshine duration, and solar radiation, whereas decreases occurred in spring cloudiness and winter precipitates. These changes resulted in altered light regimens in the lake, which were associated with an increased availability of photosynthetically relevant radiation in springtime. In combination with an increased biogenic matter load, this could lead to drastic changes in the structure of phytoplanktonic communities and in their seasonal successions, as well as in biogenic matter dynamics. Based on these considerations and published data, a conceptual model of the emergence and development of regular harmful algal blooms in the lake Imandra is suggested.