Per the vendor, "These food containers are not weatherproof or air tight. There are no seals or gaskets around the edge of the lids. They are snap shut closures only. We also do not recommend that they be stored in the outside areas. Placing them for storage in a dry place, such as a shed or garage, would be a better way to keep them from getting moisture in and ruining the food that is being stored in them."

Unfortunately, you cannot stack different sizes on each other. There are grooves molded into the tops of the bin to align the feet on the bottom of the storage bins to help secure the top bin that will not align with other sizes.