1. A memory system comprising: a plurality of non-volatile memories; one or more temperature sensors each of which is disposed in or adjacent to one of the non-volatile memories; and a controller for the plurality of non-volatile memories, that is configured to maintain a temperature increase amount and a reference temperature for each of the non-volatile memories, select one of the non-volatile memories having a pending command as a next memory to be accessed based on a current temperature, the temperature increase amount, and the reference temperature of the selected non-volatile memory, and access the selected non-volatile memory to perform the pending command.