The timer is an electronic device and is not subject to freezing problems. I'm not sure, but it could be affected by moisture. I would locate it as close to the manifold where the valves are as is possible/practical. Cut down on the wire runs as much as possible, and keep it as simple as possible. This might not work for you, but mine is on my basement wall and the manifold is on the outside of the same wall directly opposite. The wire lengths are less than 4' each and nothing is buried. I must be OK, it's been working fine for 25 years.