I got a crock pot and a paint brush and I've been planning to drive down to my bees tonight, open up the top hive box, remove the unused frames, coat them in wax, then return them to the hive the next morning. This is to encourage a slow hive to build comb. The only problem is: it's cloudy and showery today, and it's going to be even more showery tomorrow. Is the reason that you're not supposed to open up hives when it's raining because you don't want water to get in there? And the entire hive is inside rather than out foraging, and in a grumpy mood? If it's probable that there aren't any/many bees in the top box anyway (which would be the only part I'm opening up), and I had a friend hold a big umbrella over the hive, is that a viable workaround, or is that completely stupid?