Northern and tundra forest ecosystems are especially vulnerable to climate impact because of their high sensitivity to changes in temperature. An important issue is how the growth and productivity of the main forest-forming species in the permafrost zone of Siberia are changing under conditions of current climate change. In this study, the Vaganov-Shashkin imitation model of tree growth (the VS-model) has been used to estimate the effect of climatic factors on the growth of Cajander larch (Larix cajanderi Mayr.) in northeastern Yakutia and Dahurian larch (Larix gmelinii Rupr. (Rupr.) in the east of Taimyr) with a 1-day time resolution and to determine the extent to which the interaction of climatic parameters (temperature/precipitation) and physiological processes is reflected in the width and anatomical structure of tree rings. Despite the location of the study sites in northern regions with harsh conditions, where temperature is the main limiting factor, we have managed to identify the days of the growing season on which soil moisture had a greater impact on the growth of trees than air temperature.