Even though my controller was in my garage, I ended up installing it inside this Orbit weatherproof box:
https://www.amazon.com/dp/B000VYGMF2
The box is lockable, comes with a GFCI receptacle so you can weatherproof your transformer (I replaced the GFCI receptacle with a regular one), has two knockouts for power and signal wires. It even has a false bottom so that you easily screw your Open Sprinkler boxes onto the bottom and not worry about poking through the back.
