Yes these units can sit outside in the rain and snow. Do not place them under a pool deck. The manual states that they should be placed outdoors unobstructed. If you had to put it in some sort of enclosure, they recommend that you add a stack to it to help exhaust it properly. For winter use, some folks disconnect and take in a garage or you can get a cover for it such as a BBQ grill over or even a blue tarp. Secure it down and you're good to go. Keep in mind though it does make a nice house for mice so put some mothballs inside before wrapping it up.
Personally, I would look at the Raypak units over the Hayward. Much simpler design and no extra parts that can break and need repair down the road. If you do some searching here on this site you will see the issues people have with the Hayward's.