THE FOLLOWING HAS BEEN UPDATED SINCE ORIGINALLY POSTED.
This kind of humidity probably wouldn’t be an issue if I could find a screened bottom board or a screened inner cover somewhere. Or I suppose I could try to build one.
Imagine how difficult it is to dry honey inside such a humid hive. My ventilation rim helps, but a screen bottom board would probably help out even more.
UPDATE: The ventilation rims pull moisture from the hive by allowing an air current to flow over the inner cover hole. But as you can see in the video, humidity can still build up inside the hive underneath the inner cover. So here’s a little something I do with my hives when I know we’re in for some sunny days:
I pry up the inner covers just a bit and slide Popsicle sticks through the corners of the hive. This allows more hot air and humidity trapped under the inner cover to escape, yet the crack is small enough to prevent predatory insects like wasps from getting in. Another simple, cheap and effective beekeeping tip brought to by the good folks at Mud Songs.
UPDATE (August 20/11): I put my hand in front of the entrances of all the hives today, no entrance reducers on the hives, and I could feel the humidity pumping out of every one of them. I’m convinced now that all Langstroth hives in St. John’s, Newfoundland, even nucs, would benefit from as much ventilation as possible at least during the month of August. That means: 1) Screened bottom board, 2) Ventilated inner cover, 3) Ventilation rim. Those three together would be dynamite. Add to it a slatted rack and follower boards (aka dummy boards) and the hives will be boiling over with healthy bees and tons of honey. That’s my best guess, anyway.