During the brutal winter months, it may not be wise to leave your wooden bench exposed to the elements. While sealed hardwood can be protected against the snow and wind, depending on where you live, blizzards and snow storms can be ferocious. As such, if you do not feel like disassembling your bench to store it away for the winter, perhaps you could opt for a protective cover instead.
This is only for precautions, but this can keep dust, rain, snow, and other elements off of your bench. But, make sure that the covers are breathable as you do not want moisture building up inside as this can lead to mold and mildew. If you take a trip to Amazon, you are sure to find several bench covers that will more than suffice.