We analyzed long-term (1958–2017) data on variations in the numbers of the bank vole (Myodes glareolus Schr.) in Eastern Fennoscandia, which is the northern periphery of the species distribution range. The species abundance under these conditions is relatively low compared to the optimum range (1.9 voles per 100 trap-days or 1.7 voles per 10 pitfall-days), but the species remains a leader in the total small mammal population, accounting for 50.5 % of catches by trap lines and for about 10 % of catches by pitfalls, where it is second in abundance only to common shrews. Pronounced long-term changes in abundance have been revealed, with a significant amplitude of fluctuations and an irregular alternation of short-term and quite high rises and prolonged and deep lows. Itwas found that in contrast to the optimum range, where a major regulator is intrapopulation compensatory mechanisms, this function in the northern periphery is performed by external, mainly weather-phenological factors, which in the North are extreme in scope and irregular in manifestation. It can be concluded from the analysis of the materials that among all the versatile factors determining the environmental situation of the year, the key spring onset, temperature and the amount of precipitation in late spring-early summer, and the yield of coniferous seeds (largely responsible for the foraging conditions in winter).