For almost all of the models on our list, you can leave them out in the rain. These units are typically made from a durable metal such as stainless steel or aluminum that are impervious to rust. However, if you want to make sure that you unit stays in the best condition possible, it is for the best that you remember to bring it back inside your storage shed when you are done using it. While it is ok to accidentally leave it outside for a few times, persistent exposure to rainfall may negatively impact the quality of your handle over time. As with any type of tool, to ensure that it will last for the long haul, you will want to make sure that you take really good care of it, and that includes taking it in out of the rain when you are finished planting all of your flowers for the upcoming growing season.