Remote Relay box (waterproof)

I'm working on a Christmas light project. I have seen time and time again where a person sets it all up in one box and then has to run separate power cables to every individual group of lights on the same relay.

I want to build a small (less than 3"x3"x3" ) box for each relay which will be connected to each string itself and have a 24G twisted pair to provide control for each relay.

Now that I have explained my plan, maybe someone could help me with an idea of the small enclosure I could build to put each relay in.

Any help would be much appreciated.

Buy enclosures that have at least IP54. Use cable glands and sheathed cables, not separate leads.

for 5v relays that can handle 10A at 220ac will i have an heat related issues with such a small container?

No, i do not think they will.