I would not trust it to be dry enough to be workable. It can be safe but if not totally dry, it can give some problems. I use a lot of cedar in my tanks but it is wood that I find and pick very carefully. Many people do not understand that there is dry and TOTALLY dry. Cedar is famous for lasting when exposed to weather because it does retain the oils and sap better than many woods. Along with these, you will find tannins. Depending on your local water, it can give you fits with PH changes. For cedar, I should think 10-15 years of weathering for it to be easy to use. But the correct cedar can be used.