Optimal Storage Temp for Liquor

[Montresor]

I have a room in my home to which I am considering a move of my supply of various whiskeys, vodka, gin, and the like. The room, however, is not climate-controlled and is somewhat prone to whatever the outside temperature is at the time. Not to any extremes, mind you, but during winter, the room will be decidedly cooler, with the opposite effect during the summer. It will never really be "room temperature."

Is it safe to the liquors here? What is the optimum temperature for storage, and at what point (hot or cold) will temperature have a deleterious effect?