1. Frost hollows (FH) are small, confined lichen-dominated ecosystems surrounded by lichen woodlands. FH are impacted by repetitive frosts occurring during the growing season. We evaluated the dynamics of FH across the boreal forest in eastern Canada and assessed the influence of latitude as the main geoclimatic factor controlling their development. 2. The distribution and abundance of FH along 39 longitudinal transects were based on aerial photographs and field validation. Black spruce (Picea mariana) in FH and adjacent woodlands were sampled for age determination, year of tree establishment, height growth rate of spruce, and intensity and frequency of frost rings. 3. Most FH are located in the southern part of the boreal forest, in depressions bordered by dry, open, lichen woodlands. The inception and development of FH are not dependent on latitude but rather on the presence of lichen woodlands. Frost-induced thúfurs and frost rings were more frequent and abundant in the southernmost FH, whereas the northernmost FH were devoid of thúfurs. Black spruce established synchronously in FH across the boreal forest, an indication of a climatic control associated with cloudier, humid conditions reducing radiative frost activity. Most FH spruce established after 1933 and peaked in the 1980s. Fewer frost events were recorded in the 1980s than in the 1990s. In the latter decade, frost events became more frequent, intense and synchronous across the boreal forest. 4. Synthesis. The distribution of frost hollows (FH) is related to the presence of dry lichen woodlands that exacerbate frost activity during the growing season. Synchronous frost-ring frequency across the biome also suggests that shared climatic conditions, in particular freezing temperature, humidity and cloudiness, are at the origin of the dynamics of FH. A longer growing season creates propitious conditions for a higher frequency of frost events and more intense soil cryoturbation. FH are climate-sensitive ecosystems which can be used as proxies of the impact of global change on the boreal biome.