Embodiments of the present disclosure relate to a memory system and an operating method thereof. According to the embodiments of the present disclosure, the memory system may repeatedly execute, when entering a low power mode, iterations of a target operation according to a temperature of the memory system until a stop condition is satisfied. In this case, the target operation may be a garbage collection operation for the plurality of memory blocks or a migration operation of moving data stored in a first area including at least one of the plurality of memory blocks to a second area including at least one of the plurality of memory blocks. The operation speed of the memory block included in the first area may be higher than the operation speed of the memory block included in the second area.