Jay's got it. As long as your temperature doesn't drop below room temperature it's impossible for condensation to form. Since I use a radiator to cool my water it technically can only get as cold as the air around it.
If you become totally paranoid or decide to use extreme cooling like a peltier then I suggest you do some homework and check out some of the forms on the main page under Peltiers. There you can find lots of info about how to prevent condensation. It can become quite a project and involves protecting your cpu in an airtight bundle of silicone and foam. The theory there is No air, No condensation. As I said, since it looks like you got some time before you try watercooling do some reading, it will make your install easier and faster when you get that far.