One of the things I am committed to is not using paints, stains, or sealers on my Bee Tree Hives. So, even though the western red cedar I use for their construction is highly weatherproof in itself, I still coat the tops of the Hive Covers, on my own hives, with a natural sealer: beeswax!
The sun is so intense here, at 7,000' in the heart of the Rockies, that I can melt beeswax into the tops of the Hive Covers on any sunny, hot day.
(By the way, this is all done while the hive is occupied by a colony. There is no disruption to the bees at all.)
I start by simply laying empty comb on top of the Hive Cover.
The sun completely melts the beeswax. In this next photo, you can see how the comb from the photo above is beginning to melt and soak into the wood. During the melting process, I will occasionally use a flat stick as a spatula to evenly spread the melting wax around the entire surface.
I leave this for a couple of days, and then on another hot, sunny day, while the wax is melted, I scrape off the excess. Any impurities in the wax are left sitting on the surface and are easily scraped off. I end up with a clean, beautiful finish.
The result is a weatherproof coating.